大中型危险化学品仓库应与周围公共建筑物、交通干线、工矿企业等至少保持 ()m的距离。
A. 500
B. 1000
C. 2000
D. 1500
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索赔文件提交后，请求和催促建设单位在()内给予答复。
A. 10天
B. 15天
C. 20天
D. 28天
只能承受径向载荷，高速时，滚动体离心力较大，发热较严重，寿命较低，具有这种特性的轴承是()。
A. 向心球轴承
B. 圆锥滚子轴承
C. 推力球轴承
D. 滚针轴承
by no means in the first paragraph means______.
A. without doubt
B. hardly not
C. probably not
D. in no way
subtle visual traps(Para. 1) are______.
A. places where the police hide in order to trap motorists
B. parts of the road which are deceptive to the driver's eyes
C. danger spots such as sharp comers and cross-roads
D. places where there arc too many road-signs
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