Select the most appropriate option to substitute the highlighted segment in the given sentence.
You must return back the book you borrowed last month.

Correct option is B

The correct substitution of the highlighted words is (b) must return.
Explanation: The word “return” already means “to give back.” Hence, using “back” after “return” is redundant.
Correct sentence: You must return the book you borrowed last month.
Grammatical rule used:
Avoid redundancy — do not use two words with the same meaning unnecessarily.
Example: He entered the room.
Information Booster:
Other examples of redundancy:
· "Repeat again" → just "repeat"
· "Advance planning" → just "planning"