Research shows that the mound builders at Cahokia…

The mound builders built mounds at Cahokia.

Explanation:

Research made by historians shows that the mound builders are the ancient people who built mound at Cahokia city. This was the large man made structure built by mound builders for the beautification of this city. At the beginning i. e. in 7th century, there are about 1000 people living in this city but the population exceeds to 10000 people in 11th century.

populist movement, in u.s. history, politically oriented coalition of agrarian reformers in the middle west and south that advocated a wide range of economic and political legislation in the late 19th century. thus in 1892 their leaders organized the populist, or people's, party, and the farmers' alliances melted away.

the correct answer would in fact be b. (: