矿用电机车的牵引力由（）决定。
A、牵引电动机功率
B、机车与轨道之间的粘着力
C、A和B共同
D、摩擦力
参考答案：B
.________ that he had wasted a lot of time, Tom decided to work hard on his study.
A． Realizing
B．To realize
C．Realized
D．Having been realized
（）是（）对西方音乐的最重要贡献
