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问题 选择题

在等比数列{an}中，a1，a10是方程x2-x-6=0的两根，则a4•a7=（　　）

A．1

B．-1

C．6

D．-6

答案

由题意可得a1 a10=-6，则a4•a7 =a1 a10=-6，

故选D．

填空题

根据句意用所给词的适当形式填空.

1. I don't know what made him laugh so _____ (excite)?

2. Andy Law will give two _____ (perform) in Nanjing this year.

3. He made a _____ (decide) not to go there this week.

4. Most international _____ (busy) letters are written in English.

5. "We are proud of your _____ (successful), Daniel." said father.
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单项选择题

（）是指中央银行通过公开买卖政府债券，吞吐基础货币，调节货币供应量活动。

A.发行国债

B.发行金融债

C.公开市场业务

D.再贴现
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