听力原文：M: Hey, Michelle. Look what I just found. Right here in the sand.W: A piece of wo

听力原文：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 in to a computer and make a pretty detailed model to... 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!

(20)

A．Collecting objects on the beach.

B．Creating computer models.

C．Mapping currents in the ocean.

D．Tracking water pollution.