《中国药典》2010年版一部规定，石膏含量测定的成分是（）
A.含水硫酸钠
B.氯化亚汞
C.含水硫酸钙
D.硫化汞
E.二硫化铁
参考答案：C
在传说中，炎帝和黄帝是 的部落联盟首领。[ ]
A、黄河流域
B、长江流域
C、珠江流域
D、淮河流域
If an attempt is made to hoist a load that exceeds the capacity of an electric winch，an overload safety device causes a circuit breaker to cut off the current to the winch motor（）.
A.when the line pull reaches the rated winch capacity
B.after the line pull exceeds the rated winch capacity
C.after a short build-up of torque
D.immediately
