Answer:
g' = 10.12m/s^2
Explanation:
In order to calculate the acceleration due to gravity at the top of the mountain, you first calculate the length of the pendulum, by using the information about the period at the sea level.
You use the following formula:
(1)
l: length of the pendulum = ?
g: acceleration due to gravity at sea level = 9.79m/s^2
T: period of the pendulum at sea level = 1.2s
You solve for l in the equation (1):

Next, you use the information about the length of the pendulum and the period at the top of the mountain, to calculate the acceleration due to gravity in such a place:

g': acceleration due to gravity at the top of the mountain
T': new period of the pendulum

The acceleration due to gravity at the top of the mountain is 10.12m/s^2
As we know that power is defined as rate of work done
so we will have

so in order to increase the power as per above formula we know that either we need to increase the work or we need to decrease the time to complete that work
So here the correct answer will be
increase the work being done or decrease the time in which the work is completed.
I believe it is C i am not sure