Answer:
Politics.
Explanation:
As per the given description of the situation, David being an insurance salesman must avoid a 'political topic or discussion' during the party with his clients, bosses, and coworkers. The chief reason behind this would be that while discussing a political topic, David's point of view might go contradictory with the other people present at the party and this contradiction may hurt their beliefs or opinions which may lead to a biased or unfavorable perception about David in their mind which is not beneficial for David's career as a salesman. Thus, he must bring in a topic that would go favorable for him to persuade more and more people to have a positive image of him as it would assist him in selling his insurance policies to them conveniently.