题目

一列简谐横波沿x轴方向传播，图甲是t=1s时的波形图，图乙是波中某振动质元位移随时间变化的振动图线(两图用同一时间起点)，则图乙可能是图甲中哪个质元的振动图线(    ) A.x=0处的质元                              B.x=1 m处的质元C.x=2 m处的质元                          D.x=3 m处的质元—Where is the post office?—It's just over there, at the end of the street. You          not miss it.A．can B．must C．may D．would