Final answer:
The Environmental Protection Agency requires that any buyer of a house built before 1978 must be alerted to the possible presence of lead.
Step-by-step explanation:
The Environmental Protection Agency requires that any buyer of a house built before 1978 must be alerted in writing to the possible presence of lead. Lead-based paint was banned by the U.S. government for use in housing in 1978, but many older homes still have this paint under newer layers. When lead-based paint deteriorates, it can expose individuals to lead.
Radon and underground storage tanks are also potential hazards in homes, but the question specifically asks for the possible presence that the buyer must be alerted to in writing, which is lead.