次级点火波形上没有火花线变长的原因是（）。
A.火花塞间隙太大
B.火花塞间隙太小
C.点火线圈阻抗过大
参考答案：A
After school we went to the reading-room to do some reading, only to be told that it .
A．was decorated
B．had decorated
C．had been decorating
D．was being decorated
风烟系统密闭何意？
