During an Emergency Such as the Three Mile Island Accident

During an emergency such as the Three Mile Island accident, neutron- absorbing rods are inserted into the reactor. What effect does this have on the thermal energy output of the reactor?

A) It has no effect on thermal energy output, because nuclear reactors create practically no thermal energy anyway.
B) Thermal energy output is unchanged for a few hours because the chain reaction takes a long time to die out.
C) Radioactivity immediately ceases, reducing the thermal energy output, but fission keeps creating thermal energy.
D) The chain reaction stops, reducing the thermal energy output, but radioactivity keeps creating thermal energy.
E) All thermal energy output immediately ceases.