Final answer:
The sentence "We waited in line for three hours because we wanted tickets to the Pentatonix concert" is a compound-complex sentence.
Step-by-step explanation:
The sentence "We waited in line for three hours because we wanted tickets to the Pentatonix concert" is an example of a compound-complex sentence structure.
Compound-complex sentences contain two or more main clauses and one or more subordinate clauses. In this sentence, "We waited in line for three hours" and "we wanted tickets to the Pentatonix concert" are the two main clauses, and "because we wanted tickets to the Pentatonix concert" is the subordinate clause.
Compound-complex sentences are effective when expressing multiple ideas in a single sentence.