Statement(A) :  In stationary waves , all particles between two nodes pass through the mean position at the same time with different velocities .

Statement(B) :  In a stationary wave, all particles are at rest at the same time twice in every period of oscillation.

In a stationary wave all the particles have same frequency so they cross the mean position at the same time but as they have different amplitude they have different velocities.

All the particles except at nodes come to rest twice in every oscillation when they are at antinode posltion.