Answer:
Option D - by adding 3, then 9, then 15, …
Explanation:
Given : Function

To find : How do the y-values of this function grow?
Solution :
From the following options the most suitable option is D.
As if we are going to add term and terms our y-values increases.
When we add any term in the function the y value value increases.
If we adding 3, then 9, then 15, … the function continuously grow term by term.
The new function became

Therefore, Option D is correct.