Because of the previous arrangements made with her professor, Carla was allowed extra time on the test, therefore, she was able to manage her test anxiety.
Because of the previous arrangements made with her professor, Carla was allowed extra time on the test, therefore, she was able to manage her test anxiety.
The correct structure for separating two independent clauses with a conjunctive adverb like 'therefore' is to use a semicolon before it and a comma after it. Thus, 'on the test; therefore,' is the correct choice.
on the test; therefore,