Which of the following conditions indicates that a can of food may potentially be spoiled?

Rust on the can indicates potential spoilage because it can compromise the integrity of the can’s seal, allowing air and contaminants to enter. This exposure can lead to the growth of bacteria or mold, resulting in spoilage. Cans are designed to last a long time, but rust signifies deterioration which is a warning sign that the contents may not be safe to consume.

The other options either suggest that the can is still sealed or indicate that it has not been compromised. An intact label is a good sign, while a can that is cold to touch may simply mean it has been stored adequately. A can making a sound when shaken is generally irrelevant to the quality of the food inside—it might indicate a liquid without any implications for spoilage. Therefore, rust is the key indicator in this scenario.