One greenhouse gas contributes $14 \%$ to total global warming and another contributes $6 \%$. These are respectively identified as

• A

  $\mathrm{N}_2 \mathrm{O}$ and $\mathrm{CO}_2$
• Correct answer
  B

  $\mathrm{CFCs}$ and $\mathrm{N}_2 \mathrm{O}$
• C

  methane and $\mathrm{CO}_2$
• D

  methane and CFCs.

Hence, the correct answer is option: 'B'.