The following is missing for the question to be complete:
1. They should indicate problems may exist
2. They should answer "unknown" to any questions about plumbing
3. They should indicate that there are known plumbing problems
4. They should note the fact that it's an older system and potential buyers should have it professionally examined
Answer: 2. They should answer "unknown" to any questions about plumbing
Explanation: Since Madison had no problems with the pipes in the water system, i.e there was nothing to indicate that there was corrosion in the pipes, she simply could not know that she needed to examine the water system as a site of potential problem. As stated, the whole house is old, and substantial problems in such a house can occur everywhere. When filling in any questionnaire or form in the place provided for the plumbing system, it should be put "unknown" because there was no external sign that the pipes were corroded. Of course, even a real estate agent does not know this, and it is always possible, before purchasing a home by a new prospective buyer, to hire one of the experts to review and evaluate what may be the breakdowns and potential issues that may affect the price of the home when buying. The prospective buyer can simply consult with an expert all the items of the home where their condition is noted as "unknown".
I think the right answer would be intercultural
