ALERT

Energetic
Observant
Intelligent
Watchful

The correct answer is: D. Watchful

Energetic means full of energy and enthusiasm.

Observant means paying close attention to what is happening around you.

Intelligent means having a high level of mental ability.

Watchful means keeping careful attention to what is happening around you, especially in order to detect danger.

In this case, the correct answer is watchful because it is the only option that describes someone who is paying close attention to what is happening around them, in order to detect danger. The other options do not describe this specific quality.