Answer
See explanation. In each reaction, the number of nucleons and the total charge must be conserved.
Work Step by Step
a. A proton changed to a neutron. The emitted particle has tiny mass and a charge of +e; it is a positron, $\beta^+$.
b. The number of nucleons in the nucleus went down by 4, and the charge by 2e. The emitted particle is an $\alpha$ particle.
c. A neutron changed to a proton. The emitted particle has tiny mass and a charge of -e; it is an electron, $\beta^-$.
