The correct options are
A Exhaustion of natural resources by hunter-gatherers.
B Nomads had to expend energy following the animals they hunted.
C Irregular food and water supply due to climate change.
D Hunter-gatherers learnt to manipulate nature to make their food.
Hunter-gatherers realised that staying in one place for a long time meant that they would exhaust plant and animal resources. The animals also would move from one place to another, and this forced the nomads who hunted them to follow them. The changing climate was also an issue as it controlled food and water. However, they learnt to manipulate nature to make their food, and this resulted in a sedentary lifestyle that led to the formation of settlements.