Select the correct ANTONYM of the underlined word to fill in the blank and complete the following sentence.

He is always active in a party but ............. in the class.

The correct answer is inert.

Step-by-step Explanation:

1. Analyze the Request: We need to find the antonym (opposite meaning) of the underlined word "active" to complete the sentence: "He is always active in a party but ............. in the class."

2. Understand the Underlined Word: The word "active" means engaging or ready to engage in physically energetic pursuits, lively, or busy.

3. Evaluate the Options:
- angry: Feeling or showing strong annoyance, displeasure, or hostility. This is not the opposite of active.
- inert: Lacking the ability or strength to move; lacking vigor; inactive or passive. This is the direct antonym of active.
- careless: Not giving sufficient attention or thought to avoiding harm or errors. This is not the opposite of active.
- naughty: Disobedient or misbehaved (typically used of children). This is not the opposite of active.

4. Conclusion: The word "inert" perfectly contrasts with "active" to show that while he is lively and energetic at parties, he is inactive or passive in class. Therefore, the correct option is "inert".