现浇水磨石嵌分格条后______h应浇水养护。
A.10
B.12
C.14
D.21
参考答案:B
He tries _______ English. And he finishes______ homework every day.
A.to learn, to do
B.learning, doing
C.to learn, doing
D.learning, to do
如图为了使物体A往左边运动,现用滑轮组来达到目的,请画出最省力的绕法.