Q. Select the most appropriate option for the following sentence. She wrote this article ________ her holiday.

Explanation:

The natural preposition to express that an action happened within a period of time is “during.” Hence: “She wrote this article during her holiday.”

Why others are less suitable:
– in: Not idiomatic with singular “holiday” for time. We say “in the holidays” (plural) or “in the holiday season,” but not “in her holiday.”
– on: Common with days/dates (on Monday) or in the fixed phrase “on holiday” (meaning away), but “on her holiday” is awkward for marking time and can be misread as topic (an article on/about her holiday).
– by: Indicates a deadline (no later than), which does not fit the intended meaning.