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问题 单项选择题

确定化学物对人类致癌性最有价值的方法是（）

A.原癌基因激活试验

B.肿瘤抑制基因灭活试验

C.外周血淋巴细胞染色体畸变试验

D.姐妹染色体交换试验（SCE.

E.肿瘤流行病学调查

答案

参考答案：E

选择题

Stage fright is a common example of _____ educators call a "lack of confidence" among students. [ ]

A. that

B. what

C. which

D. whose

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选择题

It's  very  nice _____ pictures for me.   [ ]

A. of you to draw        

B. for you to draw  

C. for you drawing      

D. of you drawing
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