When a wave travels in a medium displacement of a particle is given by ` y(x,t) =0.03sin pi (2t-0.01x)` where y and x are in metres and in seconds,The phase difference at a given instant of time between two paticles 25 m apart in the medium is
A. ` pi //8`
B. `pi//4`
C. `pi//2`
D. `pi`
