The correct option is B due to very strong crystalline lattice.
Boron has very high melting point because of its small atomic size and very strong crystalline lattice.
It forms strong covalent bonds with the neighbouring atoms. Thus boron atom are closely packed in its solid state, so a large amount of heat is needed to break the bonds between atoms.
Thus boron has an extremly high melting point. Hence, the correct answer is option (b).