If the velocity is zero at an instant,the acceleration need not be zero at that instant as in case of motion under gravity at the topmost point.how?

Q. Assertion :A particle may be momentarily at rest and yet have non-zero acceleration Reason: The zero velocity of a particle at any instant does not necessarily imply zero acceleration at that instant.

Q. Read each statement below carefully and state with reasons and examples, if it is true or false:
A particle in one-dimensional motion
(a) with zero speed at an instant may have non-zero acceleration at that instant.
(b) with zero speed may have non-zero velocity.
(c) with constant speed must have zero acceleration.
(d) with positive value of acceleration must be speeding up.

Q. Assertion :The acceleration of an object at a particular time is the slope of the velocity-time graph at that instant of time. Reason: For uniform motion acceleration is zero.

Q. Assertion: A body can have an acceleration even if its velocity is zero at a given instant of time.
Reason: A body is momentarily at rest when it reverses its direction of motion.