Answer:
b). Decrease
Explanation:
Since the coefficient of the expansion of glass is more than the mercury then in that case if we provide heat to the glass and mercury system then glass will expand more than the mercury.
So in this case the relative expansion of glass will be more so we will observe that the mercury level will go down.
Now if we cool down the system of glass and mercury then in that case the glass will contract more as we know that the coefficient of expansion is more for the glass
So in relative frame we can say that glass will contract more compare to the length of the mercury so we will observe that mercury level is going up inside the glass
So we should decrease the temperature
