An adverbial clause of reason answers the question “Why?” A reason clause is introduced by the subordinate conjunctions like because, since, and as.
Because
Because is used when the reason is the most important part of the sentence. Therefore, it is usually put after the main clause.
Example
I couldn’t come to your party because I was rather sick.The car crashed because the driver was careless.
Since and As
Since and as are...
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