Answer:
The number of freely-moving neutrons increases over time.
The fact which is true that during a fission chain reaction the number of freely-moving neutrons increases over time.
Fission chain reactions are those reactions in which released neutron from the fission of any substance will result in the further fission of other substances.
From the above discription it is clear that, due to fission process neutron is released and due to release of these neutrons, number of neutrons will increases over a time period.
Hence, option (B) is correct.
To know more about Fission chain reactions, visit the below link:
https://brainly.com/question/24892298
