In this English vocabulary question, you are asked to select the option that is most similar in meaning to the given word "Frivolous", which usually describes something silly, trivial, or lacking serious purpose or value.

Introduction / Context:
This English vocabulary question tests your understanding of synonyms, that is, words which are similar in meaning. The target word is "frivolous", a term often used in competitive exams and everyday English to describe behaviour, actions, or things that are silly, trivial, or not having any serious purpose. Being able to match such words with their closest synonyms strengthens both your comprehension and your ability to use precise language in exams and professional communication.

Given Data / Assumptions:
- The given word is "Frivolous".
- Four options are provided: "Sensible", "Puerile", "Profound", and "Serious-minded".
- Only one option should express nearly the same meaning as the word "Frivolous".
- Standard modern English dictionary meanings are assumed.

Concept / Approach:
To solve synonym questions, first understand the exact core meaning of the target word. Then, check each option and see which word overlaps best with that meaning. "Frivolous" refers to something lacking seriousness, being silly, light-minded, or concerned with unimportant things. Once this sense is clear, you can compare it with each option and eliminate those that express the opposite idea, such as seriousness or depth.

Step-by-Step Solution:
Step 1: Recall that "Frivolous" means silly, trivial, or lacking any serious purpose. Step 2: Consider "Sensible". This means wise, reasonable, and showing good judgment, which is almost the opposite of being frivolous. Step 3: Consider "Puerile". This means childish, silly, or immature, which is close to the idea of being frivolous. Step 4: Consider "Profound". This suggests deep, thoughtful, or intellectually serious, again the opposite of frivolous behaviour. Step 5: Consider "Serious-minded". This describes someone who is thoughtful and not silly, which clearly contrasts with frivolous conduct.

Verification / Alternative check:
A quick check in standard vocabulary resources shows that "Frivolous" is often explained as silly, trivial, not serious, or lacking in importance. "Puerile" is defined as childish or immature, frequently used in the sense of silly behaviour that is not suitable for adults. Other options clearly convey the idea of seriousness or depth. Therefore, "Puerile" is the only option that matches the negative, silly, and trivial tone of "Frivolous".

Why Other Options Are Wrong:
"Sensible" is wrong because it means wise and practical, which is almost the opposite of frivolous. "Profound" is wrong because it refers to deep and intense thought or feeling, again suggesting seriousness. "Serious-minded" is wrong because it describes someone who is thoughtful and not at all trivial or silly, which contradicts the meaning of "Frivolous".

Common Pitfalls:
A common mistake is to confuse "Frivolous" with rare or profound words simply because they sound sophisticated. Another error is to select an option that feels positive without checking whether it actually matches the meaning. In vocabulary questions, you must always focus on the definition, not on whether the word sounds impressive or pleasant. Reading the word in example sentences can prevent such confusion.

Final Answer:
The word that is most similar in meaning to "Frivolous" is Puerile.