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．
