At night , the demand for electricty supplied by a fission nuclear reactor decrease. how is the fission nuclear reaction controlled to avoid overproduction of electricity

almost positive it's A im not 1000% sure but it's the most probable

Explanation:

The nuclear energy is generated from the splitting of uranium atom by the bombardment of the neutrons in the nuclear fission.

The chain reaction of nuclear fission reactor is controlled by the control rods.

The chain reaction in the nuclear power plant can be controlled by using control rods of material made up boron which absorbs neutrons.

Therefore, by increasing the exposure between the fuel rods and neutrons absorbing material the fission nuclear reaction is controlled to avoid overproduction of electricity.