二类高层民用建筑耐火等级不应低于（）级。A、一 B、二 C、三 D、四

用所给单词的适当形式填空。

1. As a child the thought kept __ (occur) to me, "Who am I?"

2. Cheer up! All the signs __ (indicate) that business will get better.

3. It is time that the entertainment industry of China __ ( reform) itself.

4. However, most people have not yet ____ (grasp)what we have  been saying.

5. My uncle owns a little farm. Sometimes he __ (hire) two or three labourers to help his harvest.

下列交易形式中，（）在规避风险方面更具优越性。

A.期权交易

B.现货交易

C.期货交易

D.远期交易

音箱有以下（）几个主要性能指标。

A.阻抗

B.失真度

C.频率响应范围

D.采样频率

解放“手”的最早发明是[ ]

A．珍妮机    

B．蒸汽机    

C．内燃机    

D．飞梭

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