I think that the best answer is: b.paleo Indians relied less on hunting big animals and more on fishing and gathering food
let's look at the options:
a. paleo Indians went to war with each other on a large scale due to scarce water resources
- This could be true if it was really hot, but this was not the case. Warming did not mean a really hot climate, but less harsh: so actually, there would be more, not less water resources.
b.paleo Indians relied less on hunting big animals and more on fishing and gathering food
- this is possible ! a warmer climate would mean that there would be more possibility to fish or gather food, which would mean that people didn't have to hunt - and they would not want to hunt big animals, as it's dangerous.
c.paleo Indians faced food shortages that resulted in a lower population
-no, a warmer climate would mean more, not less, food
d.paleo Indians lost land to rising sea level's
-no, they still had a lot of land.