The prime factorization is $2016=2^5\times3^2\times7$. Since the problem is only asking us for the distinct prime factors, we have $2,3,7$. Their desired sum is then $\boxed{\textbf{(B) }12}$.
Ansexponents first. Do all of them. Then combine like terms altogether. Then solve.
<span>2/5 is close to 1/2, and it is easy to find 1/2 of 7 mentally. Half of 7 is 3.5, so Martin gave away about 3.5 pounds.</span>