ANSWER

Step-by-step explanation
The given exponential equation is

Tom is using logarithm to solve this question. Tom is expected to take logarithm of both sides of the exponential equation to a common base.
Let us say Tom took logarithm of both sides to base 10.
Then the equation becomes,

Tom needs to apply the following properties of logarithm :

to the left hand side to obtain,

The correct answer is A.