The correct answer, is in fact, A. Mississipian Indians succumbed to diseases brought into the land by Spaniard explorer Hernando De Soto.
Hernando De Soto came in contact with the Mississipian Indians, which were settled around the Mississipi valley, in 1539. Although most contact between the Spanish and Indians was peaceful, there were also confrontations. This. however, did not affect the Mississippians directly and the Spanish explorers lasted for several years, visiting the cities established along the Southeast. The problem came later on because the Indians did not have the immunity necessary to face the many new diseases that were brought by the Spanish. This caused a decimation of the Mississippian society and altered its structure that later on led also to a cultural division, as some of the Indians adapted to lifestyle forms of the Spanish and also the political structure. The loss of lives in mass, caused by the diseases brought by the Spanish, later on brought changes in the social structures and then political structures, that forced this culture to change and break into the smaller tribes of today. Because of this, the correct answer is A.