Correct Answer: Veteran

Solution : The correct choice is the fourth option .

Veteran is used for individuals who have a lot of experience in a particular field or occupation. This term is used to describe these people who have extensive knowledge and have worked in the industry for a long time, making it the correct one-word substitute for one who has a long experience in any occupation .

The meanings of the other options are as follows:

• Reverent means to show great respect and admiration.
• Practitioner is an expert who uses that knowledge as part of a profession.
• Staunch is someone who is always loyal to supporting a person.