Which material fact about a property does not need to be disclosed if the seller is unaware of it?

The correct choice refers to latent radon gas, which is considered a material fact that does not need to be disclosed if the seller is unaware of its presence. In real estate transactions, sellers are generally required to disclose known material defects or hazards. However, latent conditions are those that are not visible or obvious and can only be identified through specific testing or investigation.

Since radon gas is typically not detectable without testing, a seller who has no knowledge of its presence cannot be held responsible for failing to disclose it. This emphasizes the principle that disclosure obligations are based on the seller's knowledge at the time of the transaction. Sellers might be aware of visible damage, leaky plumbing, or structural issues, which are apparent conditions that would legally necessitate disclosure, but latent hazards like radon gas require specific testing that the seller may not have conducted or be aware of.