Evaluate the logarithm. ${\log }_5\frac{1}{125}$

A) $\sqrt{3}$
B) -3
C) 0
D) $\frac{1}{3}$
E) ${\log }_5\frac{1}{125}$ is undefined.

Remember that $\log_{5} \left(\frac{1}{125}\right) = x$ can be rewritten as $5^{x} = \frac{1}{125}$. We know that $125$ can be written as $5^{3}$, so we have $5^{x} = \frac{1}{5^{3}} = 5^{-3}$. Thus, $x = -3$. Therefore, the answer is $\boxed{\textbf{(B)}\ -3}$.