用括号内所给动词的适当形式填空。

1. Jack, one of my buddies, kept ________ (nod) his head as if he completely understood what I said.

2. Years ago we didn't know this, but recent science _________ (show)that people who don't sleep well will soon get ill.

3. He with his friends ________ (lie) in the sun and feeling relaxed on the Long Beach when his new boss called him.

4. We first met on a train in 2000. We both felt immediately that we ______ (know)each other for years.

5. Listen to the speaker carefully, or you __________ (miss) something important .

6. - The food here is nice enough.  

    - Yes,my friend ____________ (introduce) me a right place.

7. Jack told me that they ________ (return)to the USA from Shanghai by the end of next November.

8. To prevent the things getting worse, action should ___________ (take) at once.

A、B两种债券为永久性债券，每年付息，永不偿还本金。债券A的票面利率为5%，债券B的票面利率为6%，若它们的到期收益率均等于市场利率，则（）。

A．债券A的久期大于债券B的久期

B．债券A的久期小于债券B的久期

C．债券A的久期等于债券B的久期

D．无法确定债券A和B的久期大小