B) an

A) from

B) taller

A) Mohan is the cleverest boy in the class

Explanation:”Cleverest” is the superlative form of the adjective “clever” and is used to compare one person to a group, indicating that Mohan is the most clever among all the boys in the class.
Option B uses “more clever,” which is incorrect because “clever” is a one-syllable adjective, and we use the superlative form (“cleverest”) instead of “more clever.”
Option C is incorrect because “more” and “cleverest” are both used incorrectly together.
Option D is incorrect because “cleverest only” doesn’t make sense grammatically.