Answer
in general, americans with high incomes vote at
a) the same rate as any other income group
b) a lower rate than any other income group
c) a higher rate than those earning less money
d) a lower rate than those earning less money

C) a higher rate than those earning less money

Explanation:

Political scientists all over the globe have come to the conclussion that voter turnout has a direct correspondance to the income, the higher the income, the more politicallh involved the person becomes, this could also be related to the education, as a higher income is closely related to a higer education, more educated people and wealthier people tend to vote more.

the answer to your question is a. the salt plains

in 1811, he led an expedition, known as the george c. sibley expedition, to improve relations with the pawnee and kansa tribes, and also to locate the rumored jefferson's salt mountain