Final answer:
The example of a relative frequency from the provided choices is '28%,' which indicates the proportion of adults in the sample who reported going to bed after midnight.
Step-by-step explanation:
The question is asking for an example of a relative frequency from the provided choices. A relative frequency refers to how often something happens divided by all outcomes. In the context of the given study, it is the proportion of adults in the sample who go to bed after midnight.
The choice that represents a relative frequency is '28%'. This percentage indicates that out of the total sample, 28% reported going to bed after midnight. The number 140 represents the actual frequency count, which is not relative, and the number 500 is the size of the sample which is also not a relative frequency.