"Huh, explain what?" Xu Chen's hand paused, and the spoon he picked up was put back into the bowl.

The girl gave him a cold look, and said, "Didn't we fall off the cliff? Why are we here? What is this place? Who are they?"

The girl paused, and Xu Chen was happy in her heart, but this joy was broken after only a moment.

"And ...... What's the matter with your daughter-in-law?" the girl asked coldly.

"Sure enough, it's here!" Xu Chen sighed in his heart, trying to make a calm appearance.

The spoon moved again, carefully fed the girl a few bites, and after the porridge bowl was empty and rested on the table, Xu Chen took off the brocade bag hanging on his chest again, held the jade pendant in his hand, and said to Yang Ziyun: "Take out your piece too, just hold it in your hand, the partition wall has ears, be careful!"

The girl nodded knowingly, and glared at Xu Chen again, and Xu Chen turned his head away stupidly.

"Alright!" the girl also took out the jade pendant and placed it in the palm of her hand.

Xu Chen then began to say: "This is the world of cultivators, that is, those mysterious people you knew in the past, after we fell off the cliff that day, what probably happened, and when I woke up, we were already in this area." Now that I think about it, it's probably this jade pendant that brought us here!"

"How to bring?" asked Yang Ziyun.

After a few days of continuous understanding, Xu Chen also had some guesses about the reason why he appeared in this area in the first place.

"That cliff is very likely to be the entrance to this area, maybe it is the weak point of a formation, people or animals from the outside world can't pass through that formation, maybe it's because of these two jade pendants, so they helped us pass through that formation and enter this area. ”

Yang Ziyun didn't understand the so-called formation, and since Xu Chen said so, she was relieved.

"Then why am I unconscious?" the girl quickly asked.

Xu Chen replied: "At first, I didn't understand, I thought you were injured or sick, but then I went to a hospital in this city, and the doctor said that you just used a method of holding your breath, or something went wrong, so you fell unconscious." ”

"That's right! This is a turtle breathing technique taught to me by Uncle Kong, and when I am familiar with it, I will subconsciously operate when I have difficulty breathing, and then the whole person will be in a state of concentration, unconscious. ”

Yang Ziyun vaguely remembered that after falling off the cliff, she had a period of dizziness, and when she waited for her consciousness to wake up a little, she felt extremely difficult to breathe, and her body subconsciously operated this turtle breath method.

"Yes, it's breathlessness, I've been ignoring it before, probably so used to it that I've never thought about it. Xu Chen smiled happily as he spoke: "It wasn't until just now, after the test, that I understood!"

"Understood?" The girl remembered Xu Chen's indulgent laughter just now, and she was amazed, Xu Chen was an unusually calm person, and there were not many things that could make him express himself like this.

"I understand a secret! A big secret! A secret that these cultivators have studied for tens of thousands of years and still haven't been able to figure out! A secret that can give me the power to protect myself in front of the cultivators!" Xu Chen's eyes lit up, and his expression was extremely excited.

"What's the secret?" Yang Ziyun's curiosity was also mobilized by Xu Chen.

"Hehe!" Xu Chen smiled silently.

Yang Ziyun's pretty face was stiff, and she scolded coquettishly: "Don't sell it, okay?"

Xu Chen smiled proudly, then lowered his voice, and said two words with a stern expression: "Oxygen!"

"Ahh

Xu Chen hurriedly shook his head, Ruomengtong's kindergarten teacher generally taught: "No! It's not 'yang', it's 'oxygen'! It's not going to be sound, it's going to be sound!"

"Uh...... By the way, there shouldn't be that word yet, I'll write it to you!"

As he spoke, Xu Chen dipped some water in the teacup and made a few quick strokes on the desk.

"Look!

Yang Ziyun glanced at the words on the desk that she had never seen before, "gas" and "sheep", which looked weird.

"What words? are you making up?" said the girl.

Xu Chen was anxious, and patiently explained: "This is a proprietary word, it is specially designed for 'oxygen', and people nowadays don't know what oxygen is, so naturally this word has not been invented!"

"Then how do you know?" Yang Ziyun's eyelids drooped slightly, and she glanced at him.

"Of course I know! because I ......," Xu Chen said, sluggish.

Crossing this kind of thing is even more terrifying than the current world of cultivators, and as he spoke, Xu Chen couldn't go on!

Fortunately, Yang Ziyun didn't delve into it, but said angrily: "Okay, can you not show off your knowledge? Hurry up and get down to business!"

"Oh, I'll tell you about the oxygen!"

Xu Chen sorted out his thoughts for a moment, and then said: "True cultivators have strong strength, and often a true cultivator needs several or even a dozen Grandmaster Realm masters to check and balance. The number of masters of the Grandmaster Realm in the outside world is extremely limited, but the number of cultivators is quite a lot, and the cultivators who appeared in the outside world in the past and were killed by the masters of the Grandmaster Realm are actually all cultivators in the foundation building period. And on top of this, there are more powerful Jindan Stage and Yuan Infant Stage cultivators, this kind of character has the power to destroy the world and destroy the earth, burning mountains and reclamation of the sea, no problem!"

"But why do these powerful guys trap themselves in a square inch, but they still refuse to go to the outside world to compete with ordinary people for land? For thousands of years, we have only found some fairy legends from the pile of old papers about gods and monsters, why do these cultivators hide their heads and tails and hide their whereabouts?"

"The so-called single-mindedness to the Tao and not being stained with red dust is all a Taoist pretext, and all the people in the world have mortal hearts, and their desires are difficult to fill, so how can they be all people who are dedicated to asceticism? Not to mention that the population of the world of cultivators is extremely huge, and the city where we are located has 800,000 people! It is not much worse than Chang'an City in the outside world, how can so many people be all oriented to the Tao and have no desires and desires?"

"Yes, when I first learned about the mysterious people from Uncle Kong, I also had such doubts, and Uncle Kong told me at that time that the reason why these mysterious people were hiding seemed to be afraid of something......

At the beginning, Kong Ke also killed a cultivator with the skills of not entering the realm of the grandmaster, and the cultivator walked alone, and he was a second ancestor who had never seen the world, so he was taken down by Kong Ke, the first person in the realm of the grandmaster, and was captured alive, after Kong Ke asked him, he wanted to let him live, but as soon as the aura bracelet left, this person turned into a pile of stains under Kong Ke's stunned expression.

Kong Ke naturally said these things to Yang Ziyun.

"You're right, the reason why these people hide their heads and don't want to show up is indeed because they are afraid! Afraid of a toxin from the outside world, a toxin that can kill them!" Xu Chen nodded.

"Toxin, what toxin?" asked Yang Ziyun next.

Xu Chen smiled and said, "I didn't understand it before, but it wasn't until I did the test just now that I understood!"

"That toxin is oxygen!"

"What do you mean?"

Xu Chen took a sip of water, moistened his throat, and continued when Yang Ziyun's unhappy expression was just revealed: "Oxygen is a thing necessary for the survival of people in the outside world, every time we breathe, we must inhale the oxygen in the air, and then exhale the exhaust gas called carbon dioxide......"

"Speak human words!" Yang Ziyun scolded with a dark face.

"Uh...... You should treat oxygen as an alternative food that our bodies need!" Xu Chen thought about it and decided not to complicate the problem, otherwise he would have to explain complex biochemical problems such as the production of oxygen, the conversion of carbon dioxide, and the metabolism of the body.

"This kind of food is what we need, if we don't eat it, we will die, suffocate to death! And even if the person is high, he will not be able to hold it for long, just like a person holding his breath in water, no matter how high the kung fu is, there is always a maximum limit, and after that, the person will die because of lack of oxygen. ”

After Yang Ziyun listened, she roughly understood, and said, "Go on!"

"The reason I neglected oxygen was because I never thought that something as sacred and precious as oxygen could be associated with toxins. Oxygen is indeed necessary for our survival, but just like water is for fish, oxygen is just an environment to which we have adapted. ”

"If you throw a person into the water, or put a fish on the shore, it won't be long before both of them die, oxygen and water, for people and fish, can not be judged by moral concepts such as good and evil, beauty and ugliness, but are just a rational and objective law of nature!"

"Survival of the fittest is like that!"

The more Xu Chen said, the more words Yang Ziyun didn't understand, and the girl's pretty face became more and more gloomy.

At this moment, the girl felt that she had become an idiot, but at this time, there was a nasty guy next to her who was gushing about his profound knowledge, which was quite a bad feeling!

"The world of cultivators originally contained the land of the outside world, but a great change occurred 10,000 years ago!

"Now it seems that this should be just a change in the natural environment, in the world of cultivators 10,000 years ago, there was no oxygen, and they relied on something called aura to survive and practice, thus gaining great power. ”

But for some reason, the natural environment has undergone tremendous changes, and a new material, that is, oxygen, has been generated, which is inherently in conflict with the aura, and once it appears, it begins to devour the aura, and at the same time destroys the cultivation civilization supported by the aura. ”

"I don't know exactly how oxygen is produced, and it needs to be studied a lot. I think I should look around, in the soil and ore of this area, to see if there are any oxygen atoms......"

"It stands to reason that even the movement of the earth's crust will only spew out the material deep in the earth's crust, and the earth's soil already contains a large number of oxygen atoms, but there is very little oxygen stored independently......"

"Even if a chemical reaction can produce new substance, to put it bluntly, it is only the movement of atoms and the recombination of new substance......"

"If there were no oxygen atoms in the world 10,000 years ago, then it is very likely that these oxygen atoms were dropped from outer space to the earth......"

"No, these speculations need to be carefully studied, and we have to find some information about the great changes that happened 10,000 years ago......

Yang Ziyun has been putting up with it, but this annoying guy has been talking and talking about some ...... If you don't understand it at all!

If you can't bear it, then you don't need to endure it anymore!

"That's enough!" the girl roared.