Answer is: B) beta plus decay.
Beta decay is radioactive decay in which a beta ray and a neutrino are emitted from an atomic nucleus.
There are two types of beta decay: beta minus and beta plus.
In beta plus decay, a proton is converted to a neutron, positron and an electron neutrino, so mass number (A) does not change.
In this nuclear reaction, oxygen (atomic number 8) changes to nitrogen (atomic number 7), because oxygen lost one proton, mass number stays the same (A = 15).
