Which of the following must a dealer disclose?

A dealer is required to disclose all known material information about a vehicle because this obligation supports transparency in the sales process and protects consumer rights. Material information refers to any facts that could influence a buyer's decision to purchase the vehicle, including issues like past accidents, salvage titles, or significant mechanical problems. By ensuring that buyers have access to this information, dealers foster trust and promote informed decision-making, which is vital in the automotive industry.

The other options do not fulfill the comprehensive disclosure requirements mandated by law. Disclosing only information requested during a sale could lead to important details being withheld from the buyer, which is not in line with ethical sales practices. Sharing information about other vehicles on the lot may not pertain to the specific purchase and doesn't meet the obligation to disclose critical facts about the vehicle in question. Lastly, limiting disclosure solely to previous ownership history fails to encompass all aspects that might be crucial for potential buyers. Thus, the requirement to disclose all known material information ensures a fair and transparent transaction.