Person who has long experience

A. Stalwart

B. Pedantic

C. Itinerant

D. Veteran

Answer: Option D

Solution(By Examveda Team)

One word substitute is Veteran.

Stalwart: loyal, reliable, and hard-working.
Pedantic: excessively concerned with minor details or rules; overscrupulous.
Itinerant: travelling from place to place.
Veteran: a person who has had long experience in a particular field.