降水
参考答案:
在基坑开挖前,先在基坑周围埋设一定数量的滤水管,利用抽水,使地下水位降落到坑底以下,直至基础工程施工完毕为止。
怎样对普通管道进行试压?
-_______have you been away from your hometown,Janet?
-Since 5 years ago.
[ ]
A. How many
B. How long
C. How much
D. How often