Explanation: A subordinating conjunction is a word or words that join a subordinate or dependent clause (a phrase that doesn't have complete meaning on its own) with an independent clause (a sentence that has at least a subject, a verb and complements that give it complete meaning). In the given sentence we have an independent clause "the pep band started to play one of its familiar, energizing songs" and a subordinate clause "As my cheerleading squad and I began to stretch" joined by the subordinating conjunction "as."
