蓄水屋顶的水层深度一般为（）mm。
A.100～150
B.150～200
C.150～180
D.200～250
参考答案：B
Being able to speak another language fluently is a great ________ when you look for a job.[ ]
A. honour
B. advantage
C. chance
D. pleasure
兆欧表的用途是什么？
