Answer:
Part 1:
People might fear to admit that they cheat on their spouses.
People might be ashamed to admit that they change partners often, as this behavior may be considered immoral.
Part 2:
No. The margin of error only allows for random sampling error, not bias.
Step-by-step explanation:
Part 1: The answers listed above both indicate response bias, or lying. Often times, this occurs due to social stigmas associated with certain answers, hence why the results might be skewed.
Regarding the other answers: A 2673 person survey is large, and assuming it was a random sample, there's nothing wrong with that.
Part 2:
No. The margin of error controls for random sampling errors, but this won't matter if the sample you survey doesn't provide accurate responses.