She is than her sister.

  1. cleverest
  2. most clever
  3. cleverer
  4. more cleverer
Answer

C) cleverer

Do not double the comparison; "cleverer" (or "more clever") is correct. Adjectives, Adverbs & Comparison · Degrees of comparison

English MCQ · More English: Adjectives, Adverbs & Comparison MCQs · Practise