"The tough sod discouraged farming and the plains animals were too fleet of foot to provided a dependable supply of food for large numbers of pedestrians. Then the horse gave the Indian the speed and stamina needed to take advantage of the opportunity to harvest the immense quantity of food represented by the buffalo herds of North America and the herds of wild cattle that propagated so rapidly in the grasslands of both Americas. The Indians stopped farming; the work was hard, boring, and unrewarding, compared to the nomadic life." -Alfred W. Crosby
The evidence provided in the above excerpt most directly reflects which of the following changes to the lives of North American Indians?
a) horses allowed for the cultivation of previously unusable lands.
b) the buffalo would become a vital resource for the American Indians in the plains.
c) buffalo and wild cattle experienced significant population declines.
d) American Indians abandoned farming across North America.

From the information given in the question, we are informed that the Indians stopped farming as the work was hard, boring, and unrewarding, compared to the nomadic life. This means that the Indians preferred the nomadic life.

Therefore, the changes to the lives of North American Indians will be that the buffalo would become a vital resource for the American Indians in the plains.

Based on this, there'll be increase in the buffalo and wild cattles. Therefore option C is incorrect. American Indians never abandoned farming across North America.

Therefore, the correct option is B.