—________ is ten plus twenty?
—It's thirty. [ ]
A. How much
B. How many
C. What
D. How
答案:C
由于防渗、止水设施的破坏,使渗径变短,造成地基土壤()甚至冲蚀,地基摩阻力降低,而使水闸产生向下游滑动失稳的险情。
A.管涌
B.破坏
C.渗透破坏
D.流失