Controlled Nuclear Reaction

Q. Which of the following options are correct regarding controlling the rate of nuclear reaction?

1. A smaller size of fuel will have controlled rate of nuclear fission reaction
2. Controlling the energy of neutrons affects the rate of nuclear fission reaction
3. A larger size of fuel has more probability of self-sustained chain reaction
4. The constituents of the nuclear fuel determine the rate of the chain reaction

Q. In nuclear reactor, reactor will become supercritical and even explode, if multiplication factor (k)

1. is less than 1
2. is greater than 1
3. is equal to 1
4. k is irrelevant