防止触电的技术措施有（）
A、绝缘屏蔽和间距
B、接地和接零
C、漏电保护
D、采用安全电压
参考答案：A, B, C, D
Bob insisted that he____ nothing wrong and ____ from work. [ ]
A. did; won't be fired
B. had done; not be fired
C. should do; mustn't be fired
D. do; shouldn't be fired
低碳钢的含碳量应小于（）。
A、0.04%
B、0.25%
C、0.16%
