Answer:
option (c)
option (b)
Step-by-step explanation:
The formula for the time period of simple pendulum is given by

Where, L be the effective length of the pendulum and g be the acceleration due to gravity acting on the pendulum.
(i) As the elevator moves with constant velocity, then there is no change in the value of g so the period remains same. option (c)
(ii) If the elevator accelerates upwards, the acceleration acting on the pendulum increases and then the time period of the pendulum decreases.
option (b)