___________________ . Conflicts are now brewing over rivers and river basins shared by many countries around the world. This is not unexpected, given the fact that more than two hundred water bodies are shared by two or more countries. Strife over water, for example, is erupting throughout the Middle East, from the watersheds of the Nile to the Tigris and Euphrates Rivers.

The passage highlights how freshwater scarcity and the shared nature of many rivers and water bodies are leading to growing international tensions and conflicts, especially in regions like the Middle East, where countries rely on the same critical water sources.

Option C discusses water scarcity, the expense of alternatives, and escalating international tensions, while also introducing the subsequent examples of conflict. The later sentences further elaborate on these points. Therefore, it serves as an ideal opening sentence and sets the stage for the ensuing dialogues. 

Option A is a general observation; however, the passage ( or the author ) asumes that readers know that water is scarce, and this statement does not lead on to the idea of international conflicts. Hence, this option is not a proper fit.

Option B doesn’t directly connect to the reality of shared rivers or rising tensions or set up the factual tone of the rest of the paragraph.

Option D focuses on individual-level scarcity, not international tension.

Hence, option C is the best answer for this ,