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