··Structure··Section A21. Each worker puts in nearly 2 200 hours a year,_____________average, and contributes about $ 30 to GDPper hour.
A)with
B) in
C)on
D) under
22. If you have difficulty_________your bills, tell your utility company as soon as possible.
A)pay
B) paid
C) to pay
D)paying
23.__________most students own a smartphone, the school does not allow them to use it in the classroom.
A)Even though
B)In case
C)Now that
D) If only
24. The airport is usually your first stop before __________on your vacation or trip.
A)leave
B)leaving
C)left
D) to leave