What does his conduct at the conference suggest about his reputation?

The reasoning for choosing that option lies in the implications of the phrase "his conduct at the conference" and how it relates to his reputation. If the conduct mentioned was negative or inappropriate, it would logically lead to an enhancement of existing negative perceptions, thereby suggesting that it contributed to a bad reputation. This aligns with how reputations are often shaped by actions and behaviors observed by others, especially in formal settings like a conference.

The other options do not fit if we assume that the conduct in question was indeed detrimental. If his actions improved his reputation significantly or were celebrated by attendees, it would indicate a positive outcome, which is contrary to the concern expressed in the question. Moreover, claiming that it had no effect on his reputation would ignore the inherent suggestion that the conduct, whether good or bad, plays a critical role in shaping how others perceive him. Therefore, the choice that it contributed to his bad reputation accurately captures the likely outcome based on negative conduct.