1.) What flatlands extend south from Chesapeake Bay to the east coast of Florida?

Since this is not my area of expertise, I searched Google under the key words "flatlands 'east coast' 'United States'" to get these possible sources:

http://www.infoplease.com/ce6/us/A0858162.html
http://www.sfrestore.org/documents/ifp99/introgl.htm
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Use your find command to search for "flatlands" within the sites. I hope this helps. Thanks for asking.

The flatlands that extend south from Chesapeake Bay to the east coast of Florida are known as the Coastal Plain.