听力原文：W: Hi, Tom.M: Kate, I haven't seen you for weeks. Where have you been？W: In Flori

听力原文：W: Hi, Tom.

M: 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 biology 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 jelly fish.

M: Jelly-fish 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 photo of some 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.

(20)

A．Sightseeing.

B．Lying on the beach.

C．Taking photos of the beaches.

D．Scuba diving.