Question

identify the clause and function in the following sentences:as she was not there, I spoke to her sister.​

Answer 1

The clause has been underlined:
As he was not there,I spoke to his brother.
The underlined clause is subordinate clause and it is an adverb clause.
Step-by-step explanation
A clause that does the function of an adverb.

Answer 2

In the sentence "As she was not there, I spoke to her sister," the clause is "as she was not there" and it functions as the reason for the action of speaking to her sister.