铅中毒发展到一定程度主要表现（）
A.贫血
B.白血病
C.腹绞痛
D.肺心病
E.中毒性周围神经炎
参考答案：A, C, E
_________the freezing wind ,they_________ the injured man in time. They felt sorry for that.
A．Had not been for ;could reach
B．If there was not; might have reached
C．But for; might reach
D．If there hadn’t been ; could have reached
RD命令和DELTREE命令均能删除子目录，它们的主要区别是 ( )
A．DOS版本不同因而功能不同B．RD是内部命令而DEI．TREE是外部命令C．DELTREE能删除非空子目录，而RD不能D．选择开关项不同
