Where does most of the world's population tend to settle? near mountain valleys wherever the herds move near bodies of water far from potential flood zones

Right now people live typically in cities which are comparatively old, so the relevant question here is where did people choose to settle in the past.

In the past it was very important for people to live next to water sources - it was a source of drinking water, allowed defence and trade. So the correct answer is "near bodies of water"