题目

Magic shows are interesting ______ the audience does not discover how the tricks are done. A . as long as B . so that C . as if D . ever since 答案：A在运动会上的百米赛跑时，终点线上的记时员为了记时准确，在记时时应（ ）A．听到发令枪声同时按下跑表B．看到发令枪散发的白烟同时按下跑表C．听到枪声或看到白烟都可以按下跑表D．看到白烟到听到枪声之间的任一时间里按下跑表