Why Do Parking Garages Often Fail and Fall During an Earthquake

Why do parking garages often fail and fall during an earthquake?

A) Garages fall due to a lack of steel reinforcing bars.
B) Garages are made of poor quality concrete.
C) Horizontal spans across the large openings are too long to support the weight of vehicles.
D) Horizontal support beams shake off their vertical columns because they are often not well braced.
E) The vertical concrete supports are too thin to support the load.