What Was the Primary Reason That Successive U

What was the primary reason that successive U. S. presidents had not submitted the Kyoto Protocol for Senate ratification?

A) The economic cost of the agreement was prohibitively expensive
B) Not enough Senators are convinced of the science behind "global warming"
C) China and India, as major greenhouse gas emitters, are not party to the Kyoto Protocol
D) The agreement did not have any enforcement mechanisms