Here's why:
* Main Clause: "They spoke" - This is the independent clause, meaning it can stand alone as a complete sentence.
* Subordinate Clause: "before lunch" - This clause depends on the main clause for its meaning. It acts as an adverbial clause, modifying the verb "spoke" by indicating when the speaking happened.
Breakdown:
* Subordinating Conjunction: The word "before" connects the subordinate clause to the main clause.
* Function: The subordinate clause acts as an adverbial clause of time, telling us when the speaking occurred.
Therefore, the sentence has a subordinate clause (adverbial clause of time) modifying the main clause.