手枪进行分解与结合的目的是（）。
A.擦拭、上油
B.更换零件
C.检查、排除故障
D.学习武器的构造原理
参考答案：A, B, C, D
I strongly suggest you ________ your oil share, whose price is sure to go up.[ ]
A. keep on
B. hold on to
C. keep up with
D. carry out
