The correct answer is - Greenhouse gas emissions.
The Kyoto protocol was an international convention is which the focus was the reduction of the emissions of the Greenhouse gases. Most of the countries that participated agreed to reduce the Greenhouse gas emissions, and indeed some have make big steps forward in that department, but the problem is that the two biggest emitters of these gases do not commit to it.
The United States and China are the two biggest emitters of Greenhouse gases, but because they do not want to risk anything with their economies, they do not commit to the agreement. Because of this, the Greenhouse gas emissions are still way above of what they should be, and it doesn't seem that that will change any time soon unfortunately.
Answer:
natural resource is the correct answer for the question
