How did all these _________?[ ]
A. came out
B. come up
C. come across
D. come about
答案:D
从10名女生和5名男生中选出6名组成课外学习小组,如果按性别比例分层抽样,则组成此课外学习小组的概率是______.
强制循环锅炉热态启动前对应对循环水泵进行()操作。
A.疏水
B.暖泵
C.冲压
D.卸压