Correct Answer: cautious

Solution : The correct choice is the first option .

Being vigilant means keeping a careful watch for possible dangers or difficulties. The adjective cautious means a person who is careful to avoid potential problems or dangers. These words have the same meaning. The other options have other meanings.

The meanings of the other options are as follows:

• Proof refers to evidence or a demonstration that establishes the truth or validity of something.
• Burglar refers to a person who unlawfully enters buildings, typically homes, with the intent to commit theft, vandalism, or other illegal activities.
• Security refers to measures taken to protect against theft, danger, or damage.