The correct answer is Option B.
In the given sentence we are to choose the word that correctly describes how 'good' the essay is.
Option A -MORE is used when a comparison between two things is made.
Option C-MOST is used when a comparison between more than two things is made.
In the given sentence there is no such comparison being made. The sentence is about a single essay. Hence these two options are incorrect.
Option D-MUCH means a large amount and is usually used with 'better' in the comparative degree. There is no meaning of large amount or meaning of comparison in the given sentence. Hence this too is not the correct answer.
Option B-VERY is used for emphasis. This word correctly describes 'how good the essay is'. Hence Option B is the correct answer.