Correct Answer: inattentive

Solution : The correct choice is the fourth option.

When seeking an antonym for vigilant , it's essential to identify a word that represents a lack of alertness or attentiveness. Inattentive fits this criterion as it denotes a lack of attention or vigilance.

The meanings of the other options are as follows:

• Wary : This term expresses caution and wariness.
• Cautious : This term indicates careful and prudent behaviour.
• Careful : This term represents the quality of being cautious and attentive.