You're trying to improve an ad's perceived quality so it performs better during an ad auction. What change would have the least-positive impact to an ad's quality?

Raising the bid amount.

Explanation:

The user attempts to enhance the relative quality of an advertisement so that it will functioning well at the time of an auction. So, increasing the bid amount might shift the least-positive impact to that of the quality of a commercial because the user wanted to enhance the quality of commercial advertisement, that's why the following answer is correct.