单项选择题

The county is a subdivision of the state usually-but not always-containing two or more townships and several villages. New York City is so large that it is divided into five separate boroughs, each a country in its right: The Bronx, Manhattan, Brooklyn, Queens and Richmond. On the other hand, Arlington County, Virginia, just across the Potomac River from Washington, D.C., is both an urbanized and suburban area, which is not further divided.

In colonial times, why was com bread more common than wheat bread