飞机上升时，飞机的拉力平衡（）。
A.重力的第二分量和升力
B.阻力和升力
C.阻力和重力的第二分量
参考答案：C
She _______ the computer for eight years, and it is still in good condition now. [ ]
A. has had
B. has bought
C. will wait
D. has borrowed
预缩砂浆修补在铺填完成后的（）内应有人专门养护。
A、2～4d
B、4～8d
C、4～8h
D、2～4h
