The correct answer is option 4) i.e. Billions of people are affected by melting glaciers.? Option 1 can be negated from the get-go as there is nothing conclusive about this statement, the statement "Nation-states do not have environmental concerns" is no-where mentioned in the passage. The passage is just suggesting that nation-states need to rethink their carbon footprint for political concerns, if not for environmental ones.Option 2 can be negated in a similar fashion as the nation-states are only accountable for man-made emissions and reducing carbon footprint as per the passage.Option 3 can be negated as nothing is mentioned in the passage that Billions of people are responsible for man-made emissions. Option 4 follows directly from the first sentence of the passage. "The dawn of the 21st century witnessed the melting glaciers oscillating between giving too much and too little to billions of people who depend on them for freshwater." After reading this sentence we can conclude that billions of people are affected by melting glaciers as they depend on it.