Change the Exponential Expression to an Equivalent Expression Involving a Logarithm

Multiple Choice

Change the exponential expression to an equivalent expression involving a logarithm.
- $$\log _ { b } 81 = 4$$

A) $b ^ { 4 } = 81$
B) $4 ^ { b } = 81$
C) $81 ^ { 4 } = b$
D) $81 ^ { b } = 4$