（2x-1）6展开式中x2的系数为（） A．15 B．60 C．120 D．2

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问题选择题

（2x-1）⁶展开式中x²的系数为（　　）

A．15

B．60

C．120

D．240

答案

（2x-1）⁶=（-1+2x）⁶⇒T₃=C₆²（-1）⁴•（2x）²=60x²．

故选B

选择题

The voyages of travelers before the 17th century show that they were not ____ the sea even

though they didn't have modern navigational aide. [ ]

A. at the expense of

B. at the risk of

C. in the way of

D. at the mercy of

单项选择题

使用SWIFT报文为企业办理电汇时，应使用（）报文。

A、MT199

B、MT299

C、MT200

D、MT103