A、Collecting objects on the beach. B、Creating computer models. C、Mapping currents in the ocean. D、Tracking water pollution. C对话中

M:Hey, Michelle. Look what I just found. Right here in the sand.
W:A piece of wood? Oh. Driftwood. Interesting shape... Almost like some sort of modern sculpture.
M:Yeah. And feel how smooth it is.
W:Hmm, Must’ve been in the water a long time. It could’ve been drifting in the ocean currents for months, or even years.
M:In the currents? Doesn’t the wind just blow things around out there?
W:Well, sure. But the currents are always moving, too. Almost like rivers, but underwater rivers, flowing through the ocean.
M:So how do they find out where these currents go? Stick a message in a bottle and throw it in the water?
W:Don’t laugh. In fact, I was reading in a science magazine that oceanographers have released huge numbers of bottles into the ocean over the years. They wanted to map out where the currents would carry them.
M:Say, I’ll bet-after they found out where all those bottles ended up—they could enter all that data into a computer and make a pretty detailed model to show where the currents go.
W:In fact, they did. And they also found a neat way to test that model. There was a freighter carrying sneakers from a factory in Asia. It was caught in a big storm and thousands of pairs of sneakers got dumped in the Pacific Ocean.
M:Really? What a waste!
W:Yeah. Turns out, though, that hundreds of these shoes started washing up on beaches somewhere near Seattle, just about where the computer models had predicted the currents would carry them.
M: Gee. You mean all that stuff I find on the beaches might be part of some big scientific experiment? I thought it was all just trash!
5. What are the speakers mainly discussing?
6. What did the man find on the beach?
7. According to the magazine article, what did scientists put into the ocean?
8. What can be inferred from the story about the sneakers?