c. WHILE
While the job is very interesting, it's also very badly paid.
All the choices are subordinating conjunctions. These conjunctions can only be used in compound sentences or sentences with two independent clauses.
The two independent clauses are:
1) The job is very interesting.
2) It is very badly paid.
So that, as long as, and until are conjunctions which may refer to the end result or conclusion of a certain topic in the sentence.
