Answer:
Temporal adverb: early
Explanation:
Subordinating conjunction: since
Well we have two actions happening. The first is Collen went to bed early. Ok this is a temporal (time) adverb .....EARLY. Ok, this is due to the fact that Colleen will have a test tomorrow. So That is why she is going to sleep early this night, ok.... to be Ok early tomorrow to have her test well done.