用汽车示波器检测发动机的点火波形时，应该使用（）.
A.示波器探头
B.电容探头
C.阻抗匹配探头
D.专用电感探头
参考答案：B
I had no idea she was there. I met her only____. [ ]
A. as a result
B. in surprise
C. by chance
D. in a way
用以描述声波的基本物理量有哪些？其基本概念是什么？
