In the following question, select the alternative which best expresses the meaning of the idiom: "A slap on the wrist".

Introduction / Context:
Idiomatic expressions often describe situations through vivid physical images that have a figurative meaning in everyday use. The phrase a slap on the wrist appears in commentaries about crime, discipline, and public policy, especially when a penalty is considered too light. Understanding this idiom helps readers interpret criticism about inadequate punishments in news articles and discussions.

Given Data / Assumptions:
The idiom in question is a slap on the wrist. The answer choices describe different types of punishment and reactions, ranging from mild to severe. We assume that the literal image is of a light, quick slap on a person's wrist rather than a serious act of violence. The task is to map this image to its established figurative meaning in English.

Concept / Approach:
Literally, a slap on the wrist is a small, quick physical action that may sting slightly but does not cause major harm. The idiom has developed from this idea to refer to a punishment that is very light compared to the seriousness of the offence. When people say that a criminal received only a slap on the wrist, they mean the penalty was mild and not harsh enough. Therefore, the best explanation among the options is a mild punishment rather than something severe or directed at the wrong person.

Step-by-Step Solution:
Step 1: Visualize the literal action of gently slapping someone on the wrist.
Step 2: Recognize that this action is small and not extremely painful, so it does not represent heavy punishment.
Step 3: Recall typical contexts where journalists say The judge gave him only a slap on the wrist.
Step 4: Understand that such usage signals dissatisfaction about the lightness of the penalty.
Step 5: Choose the option that directly states this idea of a mild or lenient punishment.

Verification / Alternative check:
If we place the idiom in a sample sentence, the meaning becomes clearer: For such a serious fraud, the fine he received was just a slap on the wrist. It would be strange to interpret this as punishing the wrong person or hitting where it hurts most. Instead, the sentence clearly criticizes the insufficiently strong response. This rechecking through context supports the choice of a mild punishment as the correct meaning.

Why Other Options Are Wrong:
Option B, punishing the wrong person, refers to misplaced blame and is not connected to the strength of the punishment. Option C, to hit someone where it hurts the most, suggests a deeply damaging action, which is the opposite of the lightness implied by the idiom. Option D, to threaten someone, talks about warnings rather than actual penalties. Option E, a very severe sentence, directly contradicts the idiom's usual criticism of leniency. Hence, these options do not align with standard English usage.

Common Pitfalls:
Some learners may misinterpret the word slap and think only of anger or aggression, missing the important qualifier on the wrist, which suggests a small, symbolic act. Others might confuse the phrase with idioms about serious punishment. It is helpful to learn idioms in short example sentences and pay attention to the overall tone: a slap on the wrist is used when speakers feel that justice has not been strict enough.

Final Answer:
The idiom a slap on the wrist means a mild punishment.