Answer
Please see the work below.
Work Step by Step
We know that
(a) When the acceleration vector is towards right, the velocity of the particle increases. Hence, the next velocity vector $v_3$ will be greater in length than $v_2$.
(b) When the acceleration vector is towards left, then velocity of the particle decreases. Hence, the next vector $v_3$ will be smaller in length than $v_2$.
