Which statement best describes the valleys of the Ridge and Valley region? A. They are 700–800 feet below sea level.
B. They are 700–800 feet above sea level.
C. They are made mostly of limestone.
D. They are made of gorges and canyons.

C.They are made mostly of limestone.

Explanation:

Valley regions are mostly made up of limestone. the valleys of Ridge and Valley region are made up of sedimentary rock such as Limestone, dolomite, and shale. These limestone are extracted from these valley and use in the production of gypsum and other industrial products. Valleys are present  at various height above sea level.

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explanation:

question

which are human systems?

the amazon rain forest

the appalachian trail

the george washington bridge

the himalayas

the hoover dam

the north american free trade agreement