Why Didn't the U

Why didn't the U.S. Congress vote to endorse the COP21 Paris Agreement?

A) No vote was necessary since the language of COP21 made it an extension of the 1992 United Nations treaty on climate change.
B) Following the advice of environmental experts, President Obama declined to ask for Congressional approval.
C) The Congressional Republican leaders made it clear that they would not vote to endorse the agreement.
D) It actually was a European Union agreement that did not need U.S. approval.