Final answer:
The interjection in the sentence 'X-rays were discovered accidentally! Amazing!' is 'Amazing.' It stands alone as a one-word sentence and expresses emotion.
Step-by-step explanation:
In the English language, an interjection is a part of speech that shows the emotion or feeling of the author. These words or phrases can stand alone, or be placed before or after a sentence. Often, an exclamation point, or occasionally a comma, follows an interjection.
In your sentence: 'X-rays were discovered accidentally! Amazing!', the interjection is 'Amazing'. It's a one-word sentence that expresses emotion and stands on its own, separated from the other sentence by punctuation.
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