The Rocky Mountains are described as younger because the Rocky's are really two mountain chains. The older mountain chain started billions of years ago, and the younger mountain chain pushed the older mountain chain up more, only 60 millions years ago.
The Nile River, The amazon river, the Yangtze River, The Mississippi river/ Missouri River, <span>The Yenisei/Angara/Selenga River</span>
I believe the answer is A
B. convergent <span> boundary of two continental crusts </span>
The characteristic is Temperature
