Question

which best completes the sentence? longer, most long, longest mammoth cave in kentucky is the worlds ______ cave system. correct the sentence. all though bats use echolocation to hunt, them arent completly blind.

Explanation:

1. For the first sentence, we use the superlative form "longest" because we are comparing Mammoth Cave to all other cave systems in the world (a group of three or more), and "most long" is an incorrect superlative form of "long", while "longer" is for comparing only two items.
2. For the second sentence, "All though" is a misspelling of the conjunction "Although"; "them" is an object pronoun, but we need the subject pronoun "they" to act as the subject of the second clause; "completly" is a misspelling of the adverb "completely".

Answer:

1. Mammoth Cave in Kentucky is the world's longest cave system.
2. Although bats use echolocation to hunt, they aren't completely blind.