Answer:
Your answer would be B.
Explanation:
Sentence B is a compound-complex sentence. A compound-complex sentence is a compound sentence with a dependent clause.
Dependent clauses, as opposed to independent clauses, fail to stand on their own because they are not complete sentences, they do not represent a complete idea (see 1). (1) cannot stand on its own because it does not represent a complete thought, it depends on a main clause to complete its meaning.
Taking all into account, it can be said that "although college was expensive" is a dependent clause. "Leonard was determined (...) than ever" is the compound sentence linked by the coordinator so.
1) *Although college was expensive
2) Leonard was determined to get in
