Select the most appropriate option to fill in the blank.
She is a doctor _______ profession.

Correct option is D

The correct option to fill in the blank is (d) by.
Explanation: The phrase "by profession" is an idiomatic expression used to indicate someone's occupation or career.
Grammatical Rule Used: Prepositions are used to show the relationship of a noun to another word. "By" is the correct preposition to denote someone's profession.
Example: He is an engineer by profession.
Meanings of other options:
· For: Used to indicate purpose or reason. (Hindi: के लिए)
· At: Used to indicate a location or point. (Hindi: पर)
· In: Used to indicate inclusion or position. (Hindi: में)