Pl i don't understand

when nuclear fission occurs

two nuclei combine to produce a heavier nucleus.

the chain reaction that results cannot be controlled.

it is a spontaneous reaction.

it must be initiated by bombardment with neutrons.

it is a spontaneous reaction.

Explanation:

It gets squeeze together so tightly that four hydrogen nuclei combine to form one helium atom. This is called nuclear fusion. In the process some of the mass of the hydrogen atoms is converted into energy in the form of light. The same process occurs in thermonuclear (fusion) bombs.

The fusion of two nuclei lighter than iron or nickel generally releases energy while the fusion of nuclei heavier than iron or nickel absorbs energy; vice-versa for the reverse process, nuclear fission. Nuclear fusion of light elements releases the energy that causes stars to shine and hydrogen bombs to explode.

personal, she chose to do it.