In a nuclear power plant, the nuclear reaction is kept from going critical by keeping the rate of reaction safe. How do the control rods figure into this?

A. The control rods absorb the excess heat produced in the reaction.

B. The control rods absorb excess neutrons, keeping them from causing too many uranium atoms to split too quickly.

C. The control rods absorb excess uranium atoms so that the reaction doesn't happen too quickly.

D. The control rods provide additional neutrons to keep the reaction going.