Simple substitution yields
$$8 \cdot 2^{x} = 5^{0}$$
Reducing the equation gives
$$8 \cdot 2^{x} = 1$$
Dividing by 8 gives
$$2^{x}=\frac{1}{8}$$
This simply gives that $x=-3$.
Therefore, the answer is $\fbox{(B) -3}$.