The Equation That Gives the Particle Displacement of a Medium

The equation that gives the particle displacement of a medium in which there is a simple harmonic progressive wave is , where the units are SI. At t = 2 s, the velocity of a particle at x = 10 m is

A) 0.
B) 2 m/s.
C) 4/p m/s.
D) 4 m/s.
E) 8 m/s.