—Where's the bag?
—I _____ know.[ ]
A. aren't
B. am not
C. isn't
D. don't
答案:D
善杀虫止痒,为治癣痒之要药的是()
A.蛇床子
B.铅丹
C.雄黄
D.土荆皮
E.露蜂房
动圈仪表中张丝的作用是()
A.产生反作用力矩
B.支撑动圈
C.引入电流
D.引入电压