7. How does the campaign to kill the buffalo
contribute to the central ideas of the text?

Explanation:

As we the know the whole of point of the text is about the Westward expansion of America, the expansionists used various strategies to subdue the natives in an attempt to expand their control.

During this occupation the campaign to kill the buffalo was one of the many strategies used by the expansionists. It aimed at killing buffaloes at large numbers so that the natives would be affected from food supply.

Buffaloes were reared by the natives as it provided huge subsistence to their needs and daily sustenance. Killing the buffaloes at large numbers greatly affected their lives.

3 is blunder, i’m not sure about the last one but the first two look correct