Which of the following must be clearly marked if not accepted by the seller?

The correct answer is that written offers must be clearly marked if not accepted by the seller. This requirement is critical in real estate transactions because written offers represent formal proposals from buyers to purchase property. If a seller does not accept an offer, it is important to indicate this clearly to avoid any confusion or misrepresentation regarding the status of the offer. A seller's failure to communicate their decision on an offer can lead to misunderstandings or even potential legal issues if parties believe an offer is still under consideration.

In contrast, confidential agreements, inspection reports, and market analyses serve different functions in the real estate process and do not have the same requirement for marking or communication regarding acceptance or rejection. Confidential agreements are typically not intended for public disclosure, inspection reports provide information about the property's condition, and market analyses offer insight into property values, but each of these documents does not necessitate explicit marking of acceptance status in the same manner as written offers.