Final answer:
The interjection in the sentence is 'Oh'
Step-by-step explanation:
The interjection in the sentence 'Oh no, I forgot my keys!' is Oh. Interjections are words or phrases that express strong emotion or surprise, and they are usually followed by an exclamation point. In this case, 'Oh' is expressing surprise or disappointment about forgetting the keys. It adds emphasis to the feeling being expressed.
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