起重机小车运行机构包括有：电动机、（）、（）、（）和角型轴承箱及车轮组成。
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I’d like to know（）your maximum speed is.
A. how many
B. how much
C. about
D. what
根据《低压配电设计规范》，电缆在桥架内敷设时，电缆总截面面积与桥架横断面面积之比，电力电缆不应大于（），控制电缆不应大于（）
A. 30%，40%
B. 30%，35%
C. 35%，30%
D. 40%，50%
Copper is often used as an electrical conductor because it （）.
A. has high resistance at low temperatures
B. has a highly polished surface
C. is able to pass current with little opposition
D. holds insulation together well
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