The Hoover Administration()to deal with the economic crisis.
A. took effective measures
B. did not take any measure
C. asked the private sector
D. refused to take strong government actio
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升降人员或升降人员和物料用的钢丝,在一个捻距内断丝断面积与钢丝总断面积之比达到(),必须更换。
A. 20%
B. 15%
C. 10%
D. 5%
猩红热的主要传染源是().
A. 患者及带菌者
B. 恢复期患者
C. 链球菌携带者
D. 家畜
E. 蚊蝇