Answer:
Although the library was closed, I could not go home yet; I needed to wait until the librarian arrived.
Step-by-step explanation:
This is a sentence that uses two independent clauses that are punctuated by a semicolon. Joining two sentences with the use of a semicolon is one of the best ways to create a long sentence of this type. Another option is to use a conjunction to create an independent and a dependent clause. Finally, you can simply separate the two sentences by using a period.