The answer for the exercise shown above is the option B, which is:
B. log5(7)+5log5(a)
The explanation of the problem is shown below:
1. You have the following expression given in the problem above:
log5(7)(a^5)
2. To expand it, you must use the logaritms properties, as following:
log5(7)(a^5)
log5(7)+log5(a^5)
log5(7)+5log5(a)
3. Therefore, as you can see, the answer is the option B.