(D) replacing “cooler” with “more dramatic” in sentence 4
The word "cooler" is slang and creates an informal tone. By changing it to "more dramatic" the formal tone is continued all the way to the end of the passage. Option A is not a good option because contractions should not be used in formal writing. Option B will not change the formality of the paragraph. Option C is also not a good choice, changing "popular" to "top" would not change the tone to being more formal.
