Correct Answer: Uninterested

Solution : The fourth option is the correct choice.

Curious describes a state of eagerness to know or learn about something, displaying interest and inquisitiveness. On the other hand, uninterested conveys a lack of interest or enthusiasm, representing the opposite of curiosity.

The meanings of the other options are as follows:

• Passionate means showing intense or strong emotions.
• Doubtful means having uncertainty or scepticism.
• Complex means complicated or intricate.

Therefore, the correct answer is uninterested.