If We Do Nothing to Slow Our Emissions of Carbon

If we do nothing to slow our emissions of carbon dioxide and other greenhouse gases, by the end of the century the global average temperatures are predicted to increase by

A) 5 to 10 ^oC (10 to 20 ^oF)
B) 1 to 2 ^oC (2 to 4 ^oF)
C) 3 to 5 ^oC (6 to 10 ^oF)
D) less than 1 ^oC (2 ^oF)