Explanation:

- The United States (Option 1) is one of the largest historical emitters but not the current largest.

- China (Option 2) is currently the largest emitter of Greenhouse Gases (GHG) as of the time of the Emission Gap Report 2020.

- India (Option 3) is among the top emitters but does not surpass China.

- The United Kingdom (Option 4) has significantly reduced its emissions and is not the largest.

- Saudi Arabia (Option 5) is among the major oil producers but does not emit more than China.

Your answer is right: China is the largest emitter of Greenhouse Gases according to the Emission Gap Report 2020.