A、To protect themselves or attract prey. B、To make the deep sea bright and beautiful. C、To find their ways in darkness. D、To att

We’re going to go on a dive to the deep sea, and anyone that’s had that lovely opportunity knows that for about two and half hours on the way down, it’s a perfectly positively black world. [23]And we used to see the most mysterious animals out the window that you couldn’t describe: these blinking lights—a world of lighting animals, like fireflies. Dr. Edith Widder—she’s now at the Ocean Research and Conservation Association—was able to come up with a camera that could capture some of these incredible animals. That’s the light produced by animals. So, like I said: just like fireflies. There’s a flying turkey under a tree. I’m a geologist by training. But I love that. And you see, [24]some of the light they use to avoid being eaten, some they use to attract prey, but all of it, from an artistic point of view, is positively amazing. And a lot of what goes on inside. There’s a fish with glowing eyes. Just absolutely amazing.
    That’s the unknown world, and today we’ve only explored about 3 percent of what’s out there in the ocean. Already we’ve found the world’s highest mountains, the world’s deepest valleys, underwater lakes, and underwater waterfalls—a lot of that we shared with you from the stage. And in a place where we thought no life at all, we find more life, we think, and diversity and density than the tropical rainforest, which tells us that we don’t know much about this planet at all. There’s still 97 percent, and either that 97 percent is empty or just full of surprises.
    [25]But I want to jump up to shallow water now and look at some creatures that are positively amazing. This is an octopus—this is the work of Dr. Roger Hanlon at the Marine Biological Lab—and it’s just fascinating how head-foot animals can, with their incredible eyes, sense their surroundings, look at light, look at patterns. Here’s an octopus moving across the reef, finds a spot to settle down, curls up and then disappears into the background.
23. What can we find in the deep sea according to the speaker?
24. What is the function of the light produced by animals in the deep sea?
25. Why does the speaker mention an octopus in the end?