A

Step 1: Understand stationary waves. In stationary waves, there are points called nodes where there is no displacement, and between these nodes, there are antinodes where the maximum displacement occurs.
Step 2: Analyze the particles. Each particle between two nodes oscillates back and forth around the mean position (equilibrium position).
Step 3: Timing of oscillations. Since these particles are at different positions along the wave, they will all pass through the mean position at different times due to their varying speeds, depending on their position in the wave.
Conclusion: Therefore, the correct option is that all particles pass through the mean position at different times with different velocities.
Therefore, the answer is A.