Answer : 2. "China"
Explanation :

Solution: Recently, the United States and China unveiled an agreement aimed at promoting clean energy, reducing reliance on fossil fuels, and curbing emissions that contribute to global warming. This announcement is very significant because it involves the United States, historically the largest contributor to climate pollution, and China, which currently holds the title of the world's largest polluter. Combined, they are responsible for about 38% of global greenhouse gas emissions.