Answer:
C. Best... Reliable
Explanation:
A is wrong, because although "intense" can fit into the paragraph, billions of people around the world need access to clean water, not polluted water.
B is wrong, because hysterical indicates "extreme emotion", which can work, but isn't the most appropriate answer. Affordable also isn't the best answer, because you shouldn't place a monetary value on clean water.
C is correct, because the international organizations have tried to fix the issue, but people still don't have access to good, clean water.
D is wrong, because "infrequent" implies that the organizations aren't trying hard enough.
