破伤风的潜伏期一般为（）
A.3～5天
B.5～7天
C.6～12天
D.12～14天
E.14天以上
参考答案：C
The poor old man with his two daughters ___ in the street.
A．was seen to beg
B．were seen to beg
C．was seen begged
D．were seen begging
使用中的电流互感器二次回路若开路，会产生什么后果？
