用所给词的适当形式填空。

1. When I was reading, I _____ (hear)a noise in the garden.

2. When I _____ (arrive)in Shanghai, it was very hot.

3. This is an _____ (amaze) story. I like it.

4. I _____ (wait) for the bus this time yesterday.

5. Yesterday was Mother's Day, so I _____ (buy)a gift for my mother.

经济周期中的短周期平均长度约为( )，由经济学家( )提出。

A．14个月；基钦

B．40个月：基钦

C．24个月；朱格拉

D．30个月；朱格拉