Question

You must return these books latest........... Monday
(from / till / by)​

Answer 1

.........by Monday

..hope it helps you

Answer 2

You must return these books latest by Monday.

• Here, the word "by" is used as a preposition.
• Prepositions are words or groups of words used in front of a noun, pronoun, or noun phrase in a sentence.
• There are different types of prepositions like "preposition of time, direction, position, or location, etc".
• Prepositions help us tell us the direction, position, or location of the object in the sentence.