1. It was quiet ____A____ those big trucks started coming through the town. （根据句意分析）
A. before B. after C. until D. unless
2,I haven't heard from him ___B__ he went to America . （现在完成时的考点）
A, after B,since C,before D, if
3,He will not go to the cinema ___C__ he is very busy . (前后句意）
A, as B, when C, because D, fo