Help me, I don't understand

Americium-241 undergoes fission to produce three neutrons per fission event. if a neutron-absorbing material is mixed in with this sample so that the rate of neutron production drops down to 1.8 neutrons per fission event, which will be effective at achieving a critical mass? check all that apply. remove a deflective shield surrounding the sample. remove absorbent material mixed in with the sample. compress the sample of americium-241.

Stage in which a typical star has completely stopped fusion

If 3 moles of a compound use 24 j of energy in a reaction, what is the a hreaction in j/mol?