Correct Answer: Veteran

Solution : The correct choice is the third option .

A veteran is a person who has considerable experience or has been involved in a particular activity, profession, or occupation for a long time. They are highly skilled or knowledgeable due to their extensive experience.

The meanings of other words are:

• Novice : A novice refers to someone who is new to a particular activity, occupation, or situation; they lack experience and are just beginning to learn or gain expertise.
• Fastidious : It describes a person who is very attentive to and concerned about accuracy, detail, and cleanliness.
• Agnostic : It refers to someone who believes that the existence of a higher power, such as God, is unknown, uncertain, or cannot be proven.

Therefore, in the context of someone having significant experience in an occupation, the word that fits best is veteran .