用工业酒精配制饮用酒可能会因含有那种物质而有毒[ ]
A．乙酸
B．乙酸乙酯
C．甲醇
D．甲醛
答案：C
You should return the book to him ___________.[ ]
A. as fast as possible
B. as soon as possible
C. as faster as possible
D. as sooner as possible
DL-20C型电流继电器在电压不大于250V，电流不大于2A时的直流有感负荷电路(时间常数不大于5±0.75)中，断开容量为50W，在交流电路中为( )V·A。
A．100
B．350
C．250
D．200
