【正确答案】 D

【答案解析】[听力原文] W: Hi, Tom. M: Hi, Kate. I haven't seen you for weeks. Where have you been? W: In Florida. M: What? Vacationing while the rest of us have been studying on the campus in the February cold? W: Not exactly. I spent most of my time underwater. M: I don't understand. W: I was on a special field trip. I went with my marine bioloav class. M: So you went scuba diving. What were you looking for, sunken treasure? W: You might say so. The sea is full of treasures, all kinds of strange, fascinating organisms. Our class concentrated on studying plankton. M: I thought they were too small to be seen. W: That's a common misconception. The plankton covers a wide variety of freely floating plants and animals, from one-celled organisms to large ones, such as the common jellyfish. M: Jellyfish may be large enough to be seen. But they are transparent, aren't they? W: Yes, most floating plants and animals have transparent tissues. It makes them practically invisible to their enemies. M: But not invisible to your biology class, I hope. W: By concentrating, I was able to see the outlines of lots of different plants and animals. In fact, our professor even took photos of some of the small oceanic snails. M: How would the snails show up in the photo if they are transparent? W: We painted them with a harmless green dye. Since particles of the dye stuck to the tissues, the snails appeared in a green outline in the photos. M: That sounds like an interesting trip. W: It really was. M: But I think if I had been there. I'd much rather have spent my time just swimming and lying in the sun. How did Kate spend most of her time in Florida? 由对话中女士(即凯特)提到的I spent most of my time underwater. 和男士提到So you went scuba diving. 可知，答案为D。问题中的spend most of her time对应对话中的spent most of my time。scuba diving意为“戴水肺潜水”。