Hearing Tang Feng's words, Sophia covered her mouth in surprise, but her beautiful big eyes were full of surprise, obviously, for Tang Feng's proposal, this girl agreed with it in her heart, it is estimated that if it weren't for the fact that there were so many tourists around, this girl would have to give Tang Feng a big hug.

As a girl born and raised in Texas, USA, although Sophia is a girl, she can see, meet and family since she was a child, so that the adventurous spirit of the American western cowboy also flows in her bones. If Sophia had been a boy, she would have become a proper western cowboy at her age.

After a day, Sophia now regarded Tang Feng as a good friend, so she said those complaining words to Tang Feng just now, and of course, she also used this to explain to Tang Feng that she wanted to explore. So when Tang Feng proposed to explore those unknown underground tunnels, the girl was immediately excited.

Tang Feng quietly gestured a "shhh" gesture with his index finger to his mouth, and said in a low voice: "When we go back later, let's find an excuse to stay here for a while, and then go back alone, then the two of us can explore those unknown underground tunnels, how about this method?" ”

Sophia's big eyes suddenly bent into two crescents, and she nodded with a smile in agreement.

The sinkhole at one end of the underground tunnel is obviously not as interesting as the sinkhole at the other end, this sinkhole is not only small, but also devoid of flora and fauna, and looks very desolate, so it seems more appropriate to call it a cave. So they stayed here for a while, and then they clamored to go back. In particular, Mr. Smith's two bear children were only hot for three minutes, and the two bear children were the most noisy in this group.

Mr. and Mrs. Smith were obviously fond of the two children, and the cave was really not interesting, so they prepared to return after a discussion.

"Don, we're going back, are you going back with Sophia?" Mr. Smith came to Tang Feng and asked.

"Oh, Mr. Smith, I'm a little sorry, but you know, Sophia and I studied geological surveying, so we were both interested in the topography of the place, so we decided to stay here a little longer, and maybe go up there to check it out, so we definitely won't go back with you." Tang Feng's answer was seamless, and after Mr. Smith nodded and said a few words, he turned back and beckoned the tourists who had followed him to return in a group again.

With the experience of coming, there shouldn't be any problems when you go back and be led by Mr. Smith, so the tourists followed the Smiths into the underground tunnel again, while Tang Feng and Sophia, as well as Depp and Donnie in their bags, stayed.

Tang Feng and Sophia came to the sinkhole at about eight o'clock in the morning, and it took about an hour to enter the bottom of the sinkhole and enter the sinkhole through the tunnel, so it was only about ten o'clock in the morning, and if you explored that fork in the road, it would be completely timely.

After Mr. and Mrs. Smith had led the group of tourists for about five minutes, Tang Feng and Sophia sorted out the supplies they had brought with them before walking towards the tunnel.

Because he had walked through it once, he was familiar with this underground tunnel, and Tang Feng's memory had always been very good, so after walking for about twenty minutes, Tang Feng and Sophia came to that fork in the road.

There were also several forks in the road along the way, but Tang Feng didn't stop, and Sophia of course wanted to follow Tang Feng, so she didn't complain at all. When she came to this fork in the road, which was not very big, and saw Tang Feng actually stop, Sophia asked a little nervously: "Tang, are we going to explore this fork in the road?" ”

Tang Feng nodded, shone the fork in the road with a flashlight, said "follow me", and walked towards the fork in the road.

The reason why he walked in so resolutely was because Tang Feng felt the strongest feeling at this fork in the road.

As he walked, Tang Feng took out a highlighter from his backpack and casually drew a forward symbol on the wall of the cave on the fork in the road. This kind of highlighter is one of the necessary tools for Tang Feng to work underground in the past, because this kind of highlighter can make marks on the rock, and the naked eye cannot see this mark, but with a UV flashlight, you can see those marks very clearly. With these marks, Tang Feng can find a good path to advance or retreat underground, and he can also clearly identify those places that have been surveyed. Moreover, this kind of highlighter mark can be kept on the rock for three or four days, which is especially suitable for people like Tang Feng who are surveying dry resources.

This method was learned by Tang Feng after he came to the Explorer Company, and since then, this special highlighter has become an indispensable tool in Tang Feng's backpack. This time I came out from Norsman to play, and Tang Feng also brought a few highlighters, but I didn't expect it to be useful here.

"What is this? Why can't you see anything on the rock wall? Sophia naturally didn't know the function of this highlighter, so she asked curiously.

Tang Feng smiled slightly, took out two small ultraviolet flashlights from his backpack, handed one of them to Sophia, and said with a smile: "This is a special flashlight that can emit ultraviolet rays, you use it to shine a picture on the wall I just scratched." ”

Sophia obediently pressed the button on the flashlight, and a purple light suddenly shone out of the small flashlight, shining on the rock wall that Tang Feng had just marked, and a not-so-large but unusually clear fluorescent symbol immediately appeared.

"Hehe, it's fun!" Sophia said with a smile.

"It's fun, with this thing, we don't have to worry about getting lost underground! But you should turn off this ultraviolet flashlight, save a little, let's just these two ultraviolet flashlights, if there is no power, you can't see the mark I drawn. ”

Hearing this, Sophia playfully stuck out her tongue, turned off the ultraviolet flashlight, and put the ultraviolet flashlight in her shoulder bag very preciously.

The two men continued on their way, and after about half an hour, after about five or six forks in the road along the way, the tunnel began to become narrow, and the two men had to bend over, and they began to feel a little uncomfortable.

And this position has exceeded the detection range of Tang Feng when he was in the main tunnel before, but when he came here, Tang Feng's feeling became stronger and stronger.

This uncomfortable posture made Sophia complain a little, after all, the few forks in the road just now were obviously wider than this road, but after seeing Tang Feng continue to move forward without saying a word, Sophia also gritted her teeth and followed Tang Feng closely.

After walking forward for about ten minutes, the originally narrow tunnel suddenly became wider, that is, it was more spacious than the main tunnel, and the tunnel began to brighten, and it turned out that at the top of this tunnel, there were many "skylights" of different sizes, so that the outside sunlight could shine directly here!