Here's why:
* Conjunctions connect words, phrases, or clauses. "As long as" connects an independent clause (a complete thought) to a dependent clause (a thought that cannot stand alone).
* Subordinating conjunctions introduce dependent clauses. They show the relationship between the dependent clause and the independent clause.
Example:
* As long as you study hard, you will pass the exam.
* Independent clause: You will pass the exam.
* Dependent clause: As long as you study hard.
In this example, "as long as" introduces the dependent clause and indicates a condition for the independent clause.
Therefore, "as long as" functions as a subordinating conjunctional phrase.