Which best describes nuclear fission? o a nucleus spontaneously splits and absorbs energy, o two nuclei spontaneously combine and absorb energy, o a nucleus collides with a neutron and splits, releasing energy. nuclei combine to form a heavier nucleus, releasing energy

Option (a) is the correct answer.

Explanation:

When a heavy nucleus of a large element splits into small nuclei then this type of reaction is known as nuclear fission.

For example,

Energy absorbed by the nucleus of large atom causes it to split when it is striked by a neutron or a particle.

Thus, we can conclude that the statement a nucleus spontaneously splits and absorbs energy, best describes nuclear fission.

that's what i got you can count the number of atoms