抢护背水坡滑坡险情时，可在滑坡范围内间隔抢筑（）以对其加固阻滑。
A.黏土铺盖
B.黏土后戗
C.透水土撑
D.子堤
参考答案：C
梯形中位线长18cm，被一条对角线分成两段，这两段差为4cm，则梯形两底的长为______．
_____ he was tired , ____ he didn’t stop working .
A．Although ; but
B．Though; /
C．But ; /
D．Though ; but
