Which of the following is NOT an exterior moisture problem?

Droopy shingles can indicate problems with the roof's structure or installation, but they do not necessarily signify an exterior moisture issue on their own. Unlike damaged masonry, windows, and foundation issues, which can all lead to water entry and moisture accumulation in a building, droopy shingles may simply suggest that the shingles are improperly fitted or old. This condition might not directly cause moisture problems unless it leads to actual leaks or water getting under the shingles during rain. Therefore, it stands out as the option that does not represent a direct moisture problem outside of the home.