The library had been asked for months to expand its hours. Students complained they couldn't study at night because the library closed too early. Families felt limited by the brief weekend hours. Although the library staff wanted to cooperate, the city budget did not have spare funds for the extra hours. There was nothing the staff could do. What is the key idea in this passage that affects whether or not the library can be open more often?
A. The frustrated students
B. The disappointed families
C. The library staff
D. The city budget