He was a contemplative person.

Answer: Option A

Thoughtful : absorbed in or involving thought.
Careless : not giving sufficient attention or thought to avoiding harm or errors.
Over-zealous : too zealous in one's attitude or behaviour.
Mischievous : causing or showing a fondness for causing trouble in a playful way.
Contemplative : expressing or involving prolonged thought.

Synonym of Contemplative is Thoughtful