人民警察的义务来源于()。
A.人民警察的职责
B.人民警察的职权
C.法律的规定
D.国家的任用行为
参考答案:D
解析:
人民警察的义务直接决定于国家的任用行为。
There must be many people ________ for their trains at the train station because of the golden week holiday.
A. are waiting
B.waited
C.to wait
D.waiting
冷冻干燥剂由哪些系统组成?