Fill in the blank with appropriate word.
______ borrowed your grammar book? [Basic]
Correct option is A. Who
Here option A is the correct answer.
In this question, the speaker is asking about the person who borrowed the listener's grammar book. While asking questions about a person, we use the word 'Who'. Therefore we shall choose this option.
Uses of Wh-Questions:
Who: should be used to refer to the subject of a sentence.
Eg; Who borrowed your grammar book?
What: to ask for information about things and actions.
Eg; What is the matter?
Why: is used to ask for reasons and explanations.
Eg; Why did you sleep early yesterday?
How: is an adverb that means ‘in what way’ or ‘to what extent.’ It is used to introduce questions about measurements (length, breadth, height) or amounts.
Eg; How are you today?
Hence options B, C, and D are incorrect.