A population setting near a river would be be particularly vulnerable to…

Answerrecharge zone;

It is nonrenuable which means that once you have used it, it's gone forever.

When the indian plate collided with eurasian plate because it was cool 

It's either  a. chiang kai-shek and the nationalists turned against the communists and killed hundreds of them. orb. hundreds of peasants were killed in shanghai during the period of warlord rule.  if we take into account that there was warlord rule at the time, i think that it's b (not entirely sure though)just my best thoughts.