生物素分子中与亲和素结合的主要部位是（）

A.噻吩环

B.苯环

C.咪唑酮环

D.-NH-

E.羰基

补全对话。

A: Nice to meet you, Bill!

B: Me, too.

A: What's that _________ _________?

B: Oh, it's a baseball.

A: Do you like a baseball?

B: Yes,_________ _________. I have one at home. It's _________ my bed.

A: I don't _________ it. It's _________.