Which of the following correctly represents the percentage contribution of greenhouse gases to total global warming?

1. A
   Methane $20\%$, ${\text{N}}_2\text{O}$ $18\%$
2. B
   $\text{CFCs}$ $14\%$, Methane $20\%$
3. C
   ${\text{CO}}_2$ $40\%$, $\text{CFCs}$ $30\%$
4. D
   ${\text{N}}_2\text{O}$ $6\%$, ${\text{CO}}_2$ $86\%$