从方框内选择适当的句子补全对话, 其中有两项是多余的。

A: Hello, Jay. May I ask you some questions?

B: Sure!

A: ____

B: I like collecting postcards.

A: ____

B: The pictures on them. I can learn different cultures from them.

A: That's right. Many people like collecting them.

B: ____

A: Yes, I like collecting CDs.

B: Can you tell me why you like it?

A: ____

B: Do you think developing hobbies is important?

A: Yes. ____

B: But we can't spend too much time on it. We should study hard.

A: You're right.

一个质点做直线运动，初速度的大小为2m/s，末速度的大小为4m/s，则（   ）

下列划线字注音有误的一项是(　　)