Valence electrons are found:

Valence electrons are found AT THE OUTERMOST SHELL OF AN ATOM.
Valence electron refers to those electrons that are located furthest away from the nucleus of an atom, that is, they are found at the outermost shell. Valence electrons determine the chemical properties of an element and they are the only ones that get involved in chemical reactions with other elements.  

There is one s orbital, and there are three p orbitals, five d orbitals, and seven f orbitals. thus, the answer is b. do not confuse the number of orbitals in a subshell with the number of electrons the subshell can hold. each orbital can hold two electrons, so the capacity of an nf subshell is 14 electrons.