What is the longest in the United States

1.What is the longest in the United States
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2. What vehicles can travel along the Ganges for a thousand miles?
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3.The greatest rivers for navigation is ___________
A.The Mekong                      B. The Amazon
C The mississippi                 D. The Nile
4.When rivers are dammed , people use the water for_____________
A.Washing clother           C.keeping the rivers clean
B.irrigation and the production of electricity 
D.Making electricity