Answer:
The correct answer concerning a subordinate conjunction is letter b. The concert attendees roared their approval while the band played a new song.
Explanation:
Letter A can be eliminated. It joins the sentences only with a semicolon, without any conjunctions.
Letter C does use a comma and a conjunction, "so". However, "so" functions as a coordinating conjunction, not as a subordinating one.
The same goes for letter D. We have a comma and a coordinating conjunction, "and". There is actually an easy acronym to help memorize the coordinating conjunctions: FANBOYS (for, and, not, but, or, yet, so).
The only correct option is letter B. The subordinating conjunction "while" is used to establish a relationship concerning time between the two sentences. Its purpose is to show that both actions took place simultaneously.
