Definition: In this task, you're given a four sentences of story written in natural language. Your job is to complete end part of the story by predicting appropriate last sentence which is coherent with the given sentences.
Input: Sentence1: Ethan was interested in crop circles. Sentence2: He studied as much about them as he could. Sentence3: He was determined to figure out what caused them. Sentence4: But after years of studying, he had no answers.

Ethan decided crop circles would always be a mystery.