where's the rest of question so I can help?
Answer:
Option D is correct.
Step-by-step explanation:
We can tell that
Now, let's simplify.
=> 
=> 
=> 
=> 
=> 
Therefore, Option D is correct.
Hoped this helped.
Answer: a^3+81ab^2
First, you square (a+9b) which will become (a^2+81b^2)
Then, you multiply it by a and you will get a^3+81ab^2