A body describes the first half of the total distance with velocity v1 and the second half with velocity v2. The average velocity is :
(A) \(\cfrac{v_1 +v_2}{2}\)
(B) \(\cfrac{1}{v_1}+\cfrac{1}{v_2}\)
(C) \(\cfrac{v_1 \,v_2}{v_1+v_2}\)
(D) \(\cfrac{2v_1\ v_2}{v_1+v_2}\)