Final answer:
Every adverbial clause begins with a subordinating conjunction, which is a type of conjunction that connects a dependent clause to an independent clause.
Step-by-step explanation:
Every adverbial clause begins with a subordinating conjunction. An adverbial clause is a dependent clause that provides additional information about the time, place, manner, condition, etc., of the action in the main clause. It cannot stand alone as a complete sentence since it doesn't express a complete thought and generally relies on the main clause for context and meaning. For example, in the sentence 'If you chase two rabbits, you will lose them both,' the clause 'If you chase two rabbits' is an adverbial clause that begins with the subordinating conjunction 'if.'