对治疗鼠疫无效的抗生素是()
A.链霉素
B.庆大霉素
C.氯霉素
D.阿米卡星
E.青霉素
参考答案:E
― I never __________ him after he went to the USA.
―Maybe you should write to him first.
A. hear about B. hear of C. hear from D. hear out
电除尘振打器过流的原因()。
A、输入电压相角角度过大;
B、电磁锤存在卡涩现象;
C、取样线故障;
D、相控板故障。