The correct option is D The body has a uniform retardation from t=8 s to t=12 s
Displacement in 12 s = area under v−t graph
Hence (a) is incorrect.
Option (b) is incorrect because during first 3 s velocity increases from 0 to 4 m/s
Option (c) is incorrect, because in part AB, velocity is constant due to which acceleration becomes 0.
From t=8 s to t=12 s, slope is negative due to which the body is having uniform retardation.