Answer:
The best choice is the last choice.
Explanation:
There are several errors here. The first is in the first step, where the sum somehow magically becomes a product.
The next is in the next step where the product magically becomes a sum again, and the factor of 2 is distributed over the sum terms.
Finally, the terms containing "ab" and "a" are combined, even though they are not "like" terms. This is the error that has a description among the answer choices. (Blue markup)