Answer the following question given this paragraph: 

The control rods play an important role in the modulation of the nuclear chain reaction (usually a collision of a neutron with uranium). Each collision produces more neutrons than were present initially. If left unsupervised, the reaction would soon get out of control. Rods are commonly made of boron or a number of metals and metal alloys. The purpose of the control rods is to absorb neutrons to regulate the rate of the chain reaction so that the water does not overheat and destroy the reactor.


Q: What play an important role in the modulation of the nuclear chain reaction?

 Choices:

- radiation rods

- control neutrons

- particle rods

- control rods

A:
control rods
