The Number Density of Conduction Electrons in a Metal Can

Multiple Choice

The number density of conduction electrons in a metal can be found from the density r of the metal,the mass per mole M of the metal,the number of conduction electrons per metal atom,and Avogadro's number N_A.If we assume one conduction electron per atom,which of the following gives the number density of conduction electrons for a given metal?

A) N_A r M
B) N_A r /M
C) N_A M/r
D) N_A /r M