The correct option is D in all cases irrespective of whether the motion is one of uniform velocity, or of uniform acceleration or of variable acceleration
In general the area under the velocity-time graph gives the displacement happening in given time.
The area under the velocity-time graph between any two instants t=t1 and t=t2 gives the displacement in time δt=t2−t1.
This holds good for objects in uniform velocity, uniform acceleration, variable acceleration.