explain why the motion of a body which is moving with constant speed in a circular path is said to be accelerated ?

In this case when a body moves in circular path acceleration is called Centripetal acceleration... Body in circular path moves with constant speed but its direction changes at every instant of time ...as acceleration is produced when either magnitude or direction of velocity changes...here magnitude remains same but direction changes so body is said to be accelerated....

as its velocity changes and hence is known as accelarated