The nucleus that decays to produce a nucleus with one additional proton undergoes beta-plus decay. In beta-plus decay, a proton in the nucleus is transformed into a neutron, emitting a positron (which is the antimatter counterpart of an electron) and a neutrino. This process effectively decreases the number of protons in the original nucleus and increases the atomic number, resulting in a nucleus with one additional proton.
So, the correct answer is:
O beta-plus decay.