The coordinates of a particle moving in a plane are given by x(t)=acos(pt) and y(t)=bsin(pt) where a,b(<a) and p are positive constants of appropriate dimensions. Then
a. the path of the particle is an ellipse
b. the velocity and acceleration of the particle are normal to each other at t=π/(2p)
c. the acceleration of the particle is always directed towards a focus
d. the distance travelled by the particle in time interval t=0 to t=π/(2p) is a