肾盂癌的典型症状是（）
A.腰部钝痛
B.无痛性全程肉眼血尿
C.尿急，尿频
D.发热
E.无明显症状
参考答案：B
— Jack, _____ you behave yourself? You're no longer a kid.
— Sorry, Daddy. It won't happen again.
A. mustn't
B. can't
C. should
D. would
切勿将不绝缘的（）用于修理电器设施。
A、扳手
B、钳子
C、锉子
