Here's why:

* Boron-12 has 5 protons and 7 neutrons. This means it has an unstable neutron-to-proton ratio.

* Beta minus decay involves a neutron transforming into a proton, emitting an electron (beta particle) and an antineutrino.

* Carbon-12 has 6 protons and 6 neutrons. This more stable ratio is achieved by the neutron decay.

The nuclear equation for the decay is:

¹²B → ¹²C + e⁻ + ν̅ₑ

Therefore, the type of nuclear radiation emitted in Boron-12 to Carbon-12 decay is beta minus (β-) radiation.