TASK DEFINITION: In this task, you are given a sentence. You must judge whether a single noun or verb has been replaced with another word with the same part of speech. The inversion would result in the sentence sounding unnatural, So unnatural sentences will be considered changed. Label the instances as "Original" or "Changed" based on your judgment.
PROBLEM: He used to spend hours perfecting the old books . "

SOLUTION: Changed

PROBLEM: El Cid was a cog in the wheel , fighting between Christians and Muslims who serve the same deity .

SOLUTION: Original

PROBLEM: What 's the big epiphany ?

SOLUTION:
Original