From a nuclear structure standpoint, why is the hydrogen isotope deuterium used as a primary fuel source in nuclear fusion reactions?

Its nucleus lacks neutrons entirely, making it highly unstable and easy to split apart.

Its heavy mass makes it an excellent material for absorbing excess stray radiation.

Its nucleus contains one proton and one neutron, providing the necessary mass to fuse with another light nucleus.

Its electron configuration allows it to form highly volatile chemical bonds with heavy metals.