Final answer:
Sentence 25 is best revised to 'An expansion in voting might result in elections that are less polarized,' incorporating a gerund and maintaining sentence clarity.
Step-by-step explanation:
The best way to revise sentence 25 using a gerund is option (a), which reads: An expansion in voting might result in elections that are less polarized. This option effectively incorporates a gerund (voting) and also concisely communicates the idea that increasing voter participation may lead to less polarized elections.
The best way to revise sentence 25 using a gerund is option b. The revised sentence would be:
"An expanding number of voters might result in elections that are less polarized."