Answered

How did a warming climate 12,000 to 10,000 years ago impact the Paleo-Indians living in the Americas at the time?

APaleo-Indians lost land to rising sea levels.
BPaleo-Indians faced food shortages that resulted in a lower population.
CPaleo-Indians relied less on hunting big animals and more on fishing and gathering food.
DPaleo-Indians went to war with each other on a large scale due to scarce water resources.

Verified Answer :

A warming climate meant that more edible plants were available: it means that people could rely better on gathering food.

It also meant that fishing was easier for many reasons. - the correct answer  is c

It made the food generally more abundant, so it did not lead to extended wars.
Also there was still plenty of land left, so the Indians didn't loose a significant amount of land.

GeoPanther

The correct answer is - c. Paleo-Indians relied less on hunting big animals and more on fishing and gathering food.

Once the Ice Age ended, the landscape in North America changed significantly, the ice sheets melted and this allowed lots of rivers and lakes to emerge, as well as the plants to flourish in much of the continent and cover the parts that were once covered with ice. The new lakes and rivers allowed the Paleo-Indians from the interior of the continent to rely more on fishing and have fish as daily diet. The fruit trees, berries, root vegetables, that spread in most of what is now the territory of USA provided the Paleo-Indians with huge amounts of seasonal food. This two new food providers enabled the Indians to be more reliant on the nature as a food source and to not risk their lives on a daily basis while hunting some of the megafauna that roamed the North American continent.