组成人体蛋白质多肽链的基本单位是

A．L-a-氨基酸

B．D-a-氨基酸

C．L-β-氨基酸

D．D-β-氨基酸

E．L-∞氨基酸

按情景选择恰当的选项。

1. 当你想把自己的好朋友介绍给老师时，可以说：[ ]

A. Miss Zhang, this is Jenny.

B. I'm very well.

C. Hello, Jenny. Nice to meet you.

2. 你想知道爷爷今天的身体好不好时，可以问：[ ]

A. How old are you?

B. How are you today?

C. Nice to meet you.

3. 你想知道这是什么颜色的，可以问：[ ]

A. What colour is it?

B. What do they look like?

C. What's this?

4. 你知道自己考了第一名，很高兴，可以说：[ ]

A. I'm happy.

B. I'm sad.

C. I'm tired.

5. 你想告诉朋友，你爸爸是一名警官，可以说：[ ]

A. My mother is a police officer.

B. My father is a police officer.

C. My father is a bus driver.

6. 你问同学，他在做什么，可以说：[ ]

A. What is she doing?

B. What is he doing?

C. What are they doing?