A, the harmonic shear wave propagates along the positive direction of the X axis, and the waveform shifts to the right, so it is known that when t=0, the vibration direction of P particles is along the -y direction. So, A is wrong.

B, as can be seen from the figure: P and Q are half a wavelength apart, and the vibration situation is always opposite, so at time t= 1s, when the particle Q moves up through the equilibrium position for the first time, the particle P moves down through the equilibrium position, and the acceleration is zero, so B is wrong.

C, according to the waveform translation method, it can be known that the particle Q starts to vibrate downward. Because at the moment t= 1s, the particle Q with x= 10m moves upward through the equilibrium position for the first time, and the time for the particle Q to vibrate is 12T, then the time for the wave to propagate from p to q is t=T2, so t = 12× 65438.

D, the harmonic shear wave propagates along the positive direction of the X axis, and the particle E only vibrates up and down, and does not move along the X direction, so D is wrong.

So choose: C.