The correct answer is B. unimportant people.

Explanation:
The phrase "small fry" is an idiomatic expression that refers to people who are considered unimportant or insignificant in a given situation. In the context of the sentence, it suggests that only those who are seen as less important or powerless face punishment for social offenses.

- A. small boys: This is incorrect, as "small fry" doesn't specifically refer to children or boys.
- B. unimportant people: This is correct, as it aligns with the meaning of "small fry" — people who are regarded as less important or insignificant.
- C. frightened people: This is not the meaning of "small fry." The phrase does not imply fear but rather a lack of importance.
- D. frivolous people: "Small fry" does not specifically refer to frivolousness, which means lacking seriousness. It is more about importance.
- E. inexperienced people: "Small fry" does not necessarily refer to inexperience but rather to insignificance or lack of importance.

Therefore, B. unimportant people is the best option.