The dawn of the 21st century witnessed the melting glaciers oscillating…

Correct inference: Billions of people are affected by melting glaciers. The passage explicitly says glaciers are "giving too much and too little to billions of people who depend on them for fresh water," which directly supports this conclusion.

• Evidence from the passage: The phrase about glaciers affecting "billions of people who depend on them for fresh water" shows that a very large number of people are impacted by glacier changes.

• Why the other statements are not supported:

• The claim that nation-states do not have environmental concerns is not supported because the passage only says nation-states need to rethink their carbon footprint for political concerns, if not environmental ones; it does not assert absence of environmental concern.

• The claim that nation-states are responsible for providing fresh water is not stated; dependence on glacier water is described, but responsibility for provision is not addressed.

• The claim that billions of people are responsible for man-made emissions is not supported; the passage mentions man-made emissions as a cause of permafrost melt but does not attribute those emissions to billions of people.