According to the meaning of the question, the propagation distance of the wave at t=0.3s is x=3m, and the wave velocity is v = XT =10m/s. As can be seen from the figure, the wavelength λ=4m, the frequency f = v=λf = 104hz = 2.5hz from v = λ f. 。

When a and t=5s, according to x=vt, the wave propagates forward x=50m, so a is correct.

B, because the wavelength λ=4m, at X=33? Vibration of a particle at point M and vibration at point X = 1? The particle vibration at m is the same, so the velocity is along the positive direction of y axis, so b is wrong;

C, the restoring force of the particle at the equilibrium position is the smallest, so the restoring force of the particle at the wave source is the smallest, so C is correct;

D, when t=5s, the wave propagates 50m forward, so it takes 2.6s for the wave to propagate to the particle at x = 25m, so in the remaining 2.4s, the particle at x = 25m just completes the complete vibration for six cycles. Therefore, d is correct.

So choose ACD.