A:这列波沿x轴正向传播
B:这列波的波速是25m/
C:经过Δt=0.4s,A质点通过的路程是2m
D:质点P将比质点Q先第一次回到平衡位置
欧洲的内海主要包括
(____)I don't know.
(____)Where is my pencil?
(____)Li Hua, Where's your pencil?
(____)There it is.
(____)Danny, where is my pencil? Can you see it?(你看见它了吗?)