Select the option that can be used as a one-word substitute for the given group of words.
A person who is mentally ill

Correct option is B

The correct one-word substitution for a person who is mentally ill is lunatic.
Explanation: A lunatic refers to someone who is mentally ill, especially in an old-fashioned or informal sense. (Hindi meaning: पागल, विक्षिप्त)
Example: The villagers believed that the lunatic wandered the streets at night.
Meanings of other options:
· (a) Mercenary: A person who fights for money rather than loyalty (Hindi: भाड़े का सैनिक)
· (c) Psychiatrist: A doctor specializing in mental illness (Hindi: मानसिक रोग विशेषज्ञ)
· (d) Psychologist: A professional who studies the human mind and behavior (Hindi: मनोवैज्ञानिक)