Answer:
Its A i just took the test
Explanation:
A) is a complex sentence
Complex Sentence consists of 1 independent clause and 1 dependent clause.
As she was unable to swim- dependent clause (it can't be a sentence on its own)
Lena didn't want to go to the pool party- independent clause (it can be a sentence on its own)
If a dependent clause comes before the independent clause, there has to be a comma joining the 2 clauses.
I believe it is the answer A