Which sentence could the author add to the history section of “the chattahoochee river” to best support the distinctions between the uses of the river in its earlier history and in the modern era?
a
although the chattahoochee has always offered and continues to offer a source of fresh water, the river now provides a means of transportation as well.
b
although the chattahoochee has always formed natural boundaries within the state, it now is the primary source of drinking water for the citizens of the atlanta area.

c
during its earlier history, the confederate army used the shoreline to support a line of fortifications to protect atlanta; georgia now uses the river close to atlanta to support industry.

d
during its earlier history, the chattahoochee primarily served as a natural boundary, source of water, and a mode of transportation; the river now continues to offer natural boundaries and a source of water, but also supports industry and recreation.