坝体渗漏
参考答案：
水从土坝上游渗入坝体，并流向坝体下游。
The country has already sent up three unmanned spacecrafts, the most recent ________at the end of last March. [ ]
A. has been launched
B. having been launched
C. being launched
D. to be launched
1725年，天津州升为“直隶州”，下辖（）三县。
A.武清
B.静海
C.青县
