Answer is: beta plus decay (75%).
Nuclear reaction: ²⁰Na → ²⁰Ne + e⁺(positron) + ve(electron neutrino).
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 and positron and an electron neutrino, so mass number does not change.
In beta minus decay, neutron is converted to a proton and an electron and an electron antineutrino.