Transform the following sentence : You are as big a fool as a donkey.

The correct answer is D. The original sentence sets two people equal in foolishness: you and the donkey are equally big fools. The transformation has to keep that meaning while changing the form. Option D, "A donkey is not a bigger fool than you," does this. A negative comparative with "not bigger than" still allows equality, so it keeps the original sense without adding a claim that you are the bigger fool.

• Option A is wrong because "A donkey is not as foolish as you" says you are more foolish than the donkey. That reverses the meaning.
• Option B is wrong for the same reason. "Not as big a fool as you" makes you the bigger fool.
• Option C is wrong on two counts. "More foolish as" is ungrammatical, since the comparison needs "than," and the sentence claims the donkey is more foolish, which the original does not say.

The core concept is the change from positive equality ("as big a fool as") to negative comparative ("not a bigger fool than") in Transformation of Sentences. Keep the subject-object logic straight before you choose. Aspirants often pick A or B because they look more natural, but they reverse who is the bigger fool.

Trap: Choosing the option that merely sounds smoother (A or B) without checking whether it flips the direction of the comparison.