Explanation:

- Negligent: This word refers to a lack of proper care or attention. It's when someone does not take enough care in their actions.

- Option 1 - Indifferent: Being indifferent means lacking interest or concern, which is not directly related to care or attention.

- Option 2 - Strange: Strange means unusual or not familiar, unrelated to the concept of care or attention.

- Option 3 - Faithful: Faithful means being loyal or devoted, not directly opposing negligence.

- Option 4 - Careful: Careful means taking care of or paying attention to details, the opposite of negligent.

- Careful is indeed the most appropriate antonym for negligent because it directly opposes the idea of being inattentive or careless.