Preposition - Study Mode

Explanation

Solution: In this sentence, "at" is the correct preposition to use. "Candidates have to write their names at the top of the page" means they should place their names in the specific location at the uppermost part of the page. Using "in" would imply placement inside something, which does not fit in this context. "On" would suggest placement on the surface, but it is less specific than "at" when referring to the exact location at the top. "With" would suggest using something, such as writing with a pen, and does not fit in this context. Therefore, "at" is the appropriate preposition to use when referring to the specific location at the top of the page.