What would be acceleration of a body if its velocity-time graph is a line parallel to the time axis

State which of the following situations are possible and give an example of each of these:

(a) a body moving with constant acceleration but with zero velocity.

(b) a body moving in a certain direction with an acceleration in the perpendicular direction.

(a) Even when a body's velocity is zero a body can have acceleration. 

For example, when a body is thrown up, at it's highest point veocity is zero. But, the acceleration of the body is equal to acceleration due to gravity.

(b) It is possible to have acceleration in the perpendicular direction for a body moving in a certain direction. 

For example, an aeroplane moving horizontally is acted upon by acceleration due to gravity that acts vertically downwards.