Answer: D) farthest.
Explanation: Adjectives can compare two things or more than two things. To do that, we use comparative and superlative forms of adjectives. The superlative adjectives can be formed by adding "-est" at the end of the adjective (thinnest, brightest, prettiest, etc), or by writing the word "most" before the adjective (most beautiful, most boring, etc). In the case of the adjective "far" the superlative is "farthest."
