Final answer:
The example sentence 'The large amusement park was packed with people, and they had all come for the opening of a new roller coaster.' is a compound-complex sentence.
Step-by-step explanation:
The example sentence 'The large amusement park was packed with people, and they had all come for the opening of a new roller coaster.' is a compound-complex sentence. It contains two main clauses: 'The large amusement park was packed with people' and 'they had all come for the opening of a new roller coaster.' It also has one subordinate clause: 'and they had all come for the opening of a new roller coaster.'