下列哪一类毒物中毒后在两个发病期间存在一个潜伏期（）.
A.有机溶剂
B.刺激性气体
C.化学性窒息性气体
D.有机磷农药
参考答案：B
Many people think it necessary for people who are out of work ______so that they can acquire one
or more basic skills for survival in modern society. [ ]
A. be reeducated
B. being reeducated
C. to be reeducated
D. reeducated
流量控制回路属于液压系统中的（）。
A.主回路
B.辅助回路
C.过滤回路
D.动力源
______so that they can acquire one 