A．By the nineteenth century, forts were no longer used by the military.
B．Surgeons at forts could not prevent outbreaks of disease.
C．Forts were important to the development of the American West.
D．Life in nineteenth-century forts was very rough.

A．It was expensive to import product from far away.
B．Food brought in from outside was often spoiled.
C．Gardening was a way to occupy otherwise idle soldiers.
D．The soil near the forts was very fertile.