造球立轴损坏征兆是（）及（）。
参考答案：圆盘晃动；严重杂音
Something ________ otherwise he ________ here then. [ ]
A. must happen; would have been
B. must have happened; would be
C. must have happened; would have been
D. would happen; would be
A．5Hz，10A
B．50Hz，10A
C．50Hz，10 A
D．5Hz，10 A
