In the given sentence, the aim is to revise it using parallel structure to maintain consistency in the structure of the list of actions that community service helps high school students with.
Option A is the best choice for revising the sentence to use parallel structure. Here's how it achieves this:
1. "it helps them to build social awareness" - This part follows the structure of "helps them to" + verb, maintaining parallelism.
2. "taking a greater interest in their communities" - This part also follows the structure of verb + ing, maintaining parallelism.
3. "and to gain necessary job skills" - This part follows the structure of "and to" + verb, maintaining parallelism.
Therefore, by using consistent structures in the list ("to build," "taking," "to gain"), option A achieves parallel structure in the sentence.