用青霉素治疗猩红热的疗程为
A．3～5天
B．5～7天
C．7～10天
D．10～14天
E．1个月
参考答案：C
Newton was playing under an apple tree _________ an apple fell onto his head.[ ]
A. when
B. while
C. after
D. before
发电机冷却水中断超过（）保护拒动时，应手动停机。
A.60s
B.30℃
C.90℃
D.120℃
