Choose the most appropriate word meaning "suitable or intended for only young persons".

Introduction / Context:
This question tests your knowledge of words describing youth and things related to young people. The phrase in the question is suitable or intended for only young persons. The options all relate to youth, but they carry slightly different meanings. Selecting the correct one requires careful attention to usage.

Given Data / Assumptions:
The description is:

• suitable or intended for only young persons

The options are:

• Youthful
• Puerile
• Adolescent
• Juvenile

Concept / Approach:
Juvenile is commonly used for things connected with or suitable for young persons, especially children and teenagers. It can describe behaviour, literature, or products meant for the young. Youthful often describes an appearance or quality that seems young, even in older people. Puerile means childish in a negative sense, implying silliness. Adolescent usually refers to the stage of life between childhood and adulthood, and often describes people of that age.

Step-by-Step Solution:
Step 1: Note that the phrase focuses on suitability or being intended for young persons, not on simply looking young or behaving childishly. Step 2: Examine Youthful. This often describes an adult who appears young or energetic, for example youthful looks, and not necessarily something meant only for the young. Step 3: Examine Puerile. This word means childish in a foolish way, and is usually used as criticism, such as puerile jokes. Step 4: Examine Adolescent. This refers to the period of adolescence or people in that age group, but does not directly mean suitable or intended for young persons. Step 5: Examine Juvenile. This word is used for young people and can describe books, films, or behaviour directed at or typical of the young, such as juvenile literature or juvenile court. Step 6: Therefore, Juvenile best matches the sense of suitable or intended for only young persons.

Verification / Alternative check:
Consider the phrase juvenile fiction, which refers to stories written especially for children and teenagers. Juvenile products or juvenile programmes also indicate materials aimed at the young. On the other hand, youthful fashion may describe clothing that makes older people look young, not necessarily clothing exclusively for children. Puerile behaviour is foolish, and adolescent generally labels an age group. These comparisons confirm juvenile as the correct choice.

Why Other Options Are Wrong:
Youthful is wrong because it emphasises an appearance or spirit of youth, and it can apply to adults. Puerile is wrong because it carries a negative sense of being immature or silly and does not focus on suitability for young persons. Adolescent is wrong because it usually labels a phase of life or a person, not the suitability of an object or material. Only juvenile naturally fits the idea of something meant for the young.

Common Pitfalls:
Learners may choose puerile because they associate it with children, but in English it is mostly used negatively to criticise behaviour. Others may pick adolescent due to its link with teenagers, without noticing that the question is about material suitable or intended for the young. To avoid confusion, note that juvenile often appears in institutional and descriptive terms like juvenile court, juvenile justice, or juvenile books, which signal a focus on young people.

Final Answer:
The most appropriate word is Juvenile.