听力原文：M: What are you looking for？W: We're studying the basic structure of molecules.M:

听力原文：M: What are you looking for？

W: We're studying the basic structure of molecules.

M: Just any molecules？ There are quite a few of them!

W: Yes, far too many. We're only working with certain molecules that contain carbon and hydrogen.

M: What do you expect to learn from that？

W: We're trying to see the kinds of carbon molecules in which we can use silicon as a substitute.

M: What difference would that make？

W: Silicon has a lot of the same properties as carbon, hut it's much more common than carbon.

M: Oh, I see.

What is the woman studying？

A．The basic structure of atoms.

B．The basic structure of molecules.

C．The basic structure of neutron.