What happens during beta decay? A photon is ejected from a nucleus.
A helium-4 nucleus is ejected from a nucleus.
A neutron changes into a proton, or a proton changes into a neutron.
A proton changes into an electron, or an electron changes into a proton.

A neutron changes into a proton or a proton changes into a neutron

Explanation:

Here, we want to know what happens during a beta decay

In a beta decay, we have a conversion in the nucleus of an atom

Generally, there must be an excess of either the proton or a neutron in the nucleus of a radioactive atom

What we are saying here is that both do not have same values

Hence, what we have is that during a beta decay, there is a transformation of a proton to a neutron or a neutron to a proton, depending on which of the two are in excess

What this mean is that the one that changes to the other is largely dependent on which of the two is more than the other

That brings us to the principle of having a beta positive decay or a beta negative decay

the answer is c

tell me if wrong