Choose the one which can be substituted for the given sentence.
A person who has long experience in a field

Correct option is A

The correct one-word for the given group of words is (a) Veteran.
Explanation: A veteran is someone who has long experience and deep practical knowledge in a particular field; अनुभवी/ज्येष्ठ. The term implies expertise earned over time.
Example: She is a veteran teacher with three decades of classroom experience.
Meanings of the given other options:
· (b) Novice: A beginner; नवसीखिया/शिक्षार्थी.
· (c) Trainee: A person under training; प्रशिक्षु.
· (d) Amateur: One who engages in an activity for pleasure, not as a profession; शौकिया व्यक्ति (may or may not be experienced).