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问题 多项选择题

当离心泵的转速（）变化时，泵内液体流动状况保持相似，效率基本不变。

A、降低超过20%

B、降低在20%以内

C、提高超过20%

D、提高在20%以内

答案

参考答案：B, D

完形填空

How should one invest (投资) a sum of money in these days of inflation (通货膨胀)?   31   (leave) in a bank it’ll hardly keep its value, however high the interest rate. Only a brave man,  32  a very rich one, dares to buy and sell on the Stock (股票) Market. Today it seems that one of the best ways   33   (protect) your savings and even increase your wealth is to buy beautiful objects   34   the past. Here I am going to offer some advice on collecting antique clocks,   35   I personally consider are among the most interesting of antiques.

I sometimes wonder   36   a being from another planet report back about our way of life. “The planet Earth   37   (rule) by a mysterious creature that sits or stands in a room and makes a strange ticking sound. It has a face   38   twelve black marks and two hands. Men can do nothing without its permission, and it   39   (fast) its young around people’s wrists so that everywhere men go   40   are still under control. This creature is the real master of Earth and men are its slaves.”
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单项选择题

拉线施工中，拉线的方向必须是不平衡力的反方向。拉线与电杆之间的夹角一般为( )。

A．30°

B．35°

C．40°

D．45°
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