Question

join into simple sentence he was unhappy he kept himself in the room​

Answer 1

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Being unhappy, he kept himself in the room.

Explanation ↴

The process of combining two or more than two sentences into a single sentence is called Joining. Here, we have to join the two sentences into a Simple Sentence.

Here, we must use present participle because we can use participles to combine two sentences and this technique is used when both clauses have the same subject.

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Answer 2

Answer:

Being unhappy,he kept himself in the room.

Hope its help you.