Question

which type of covalent bond has two valence electrons ?
a.quadruple
b.single
c.triple
.d.double
?

Answer 1

single

Answer 2

You probably know from studying electronic structure that only two electrons can fit into an atomic orbital. It's somewhat similar for the molecular orbitals that are chemical bonds: two electrons fit into each, and so the "number" of bonds is, roughly speaking, the number of filled molecular orbitals -- which is the number of electrons divided by 2.

The general answer is considerably more complicated, but that might help you remember the connection.