A、Planktons are too small to be seen. B、Most planktons have transparent tissues. C、Most planktons are practically invisible to p

W: Hi, Tom!
M: Judy. I haven’t seen you in weeks.  Where have you been?
W: In Florida.
M: What vacationing! While the rest of us studying on the campus in February cold?
W: Not exactly.  I spent most of my time under water.
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’s full of treasures. All kinds of strange fascinating organisms. Our class concentrated on studying plankton.
M: I found plankton were too small to be seen.
W: That’s a common misconception. The term plankton covers a wild variety of freely flowing plants and animals, from microscopic one cell organisms to larger 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 planktons have transparent tissues as protected camouflage, it makes them practically invisible to predators.
M: But not invisible to your biology class, I hope.
W: By concentrating, I was able to see the outlines of lots of different plankton plants and animals. In fact, our professor even took photographs of gastropods, which are small oceanic snails.
M: How would the snails show up in the photographs of their transparence?
W: We scoured it with harmless green dye since particles of the dyes stuck to their tissues, the snails appeared in green outline in the photographs.
M: That sounds like an interesting trip. But I think if I’d been in Florida in February, I’d much rather spend my time just swimming and lying in the sun.