Concept:The correct spelling is based on the root word "prefer" and the suffix "-able", with no double "r". Explanation:Check each option carefully. Option A "Preferrable" has an extra "r". Option B "Priferable" is misspelled with "i" instead of "e". Option D "Prefarable" uses "a" instead of "e". Only option C "Preferable" follows the standard spelling from "prefer" + "able". The word means "having greater value or desirability". It is always followed by "to" (e.g., "preferable to"). Answer:C. Preferable