案例分析题Questions 22-31:The first peoples to inhabit what today is the southeastern United States sustained themselves as hunters and gathers. Sometimes early in the first millennium A.D., however, they began to cultivate corn and other crops. Gradually, as they became more skilled at gardening, they settled into permanent villages and developed a rich culture, characterized by the great earthen mounds they erected as monuments to their gods and as tombs for their distinguished dead. Most of these early mound builders were part of the Adena-Hopewell culture, which had its beginnings near the Ohio River and takes its name from sites in Ohio. The culture spread southward into the present-day states of Louisiana, Alabama, Georgia, and Florida. Its peoples became great traders, bartering jewellery, pottery, animal pelts, tools, and other goods along extensive trading networks that stretched up and down eastern North America and as far west as the Rocky Mountains.About A.D. 400, the Hopewell culture fell into decay. Over the next centuries, it was supplanted by another culture, the Mississippian, named after the river along which many of its earliest villages were located. This complex civilization dominated the Southeast from about A.D. 700 until shortly before the Europeans began arriving in the sixteenth century. At the peak of its strength, about the year 1200, it was the most advanced culture in North America. Like their Hopewell predecessors, the Mississippians became highly skilled at growing food, although on a grander scale. They developed an improved strain of corn, which could survive in wet soil and a relatively cool climate, and also learned to cultivate beans. Indeed, agriculture became so important to the Mississippians that it became closely associated with the Sun --- the guarantor of good crops. Many tribes called themselves "children of the Sun" and believed their omnipotent priest-chiefs were descendants of the great sun god.Although most Mississippians lived in small villages, many others inhabited large towns. Most of these towns boasted at least one major flat-topped mound on which stood a temple that contained a sacred flame. Only priests and those charged with guarding the flame could enter the temples. The mounds also served as ceremonial and trading sites, and at times they were used as burial grounds. Which of the following resulted from the rise of agriculture in the southeastern United States（）

A. The development of trade in North America
B. The establishment of permanent settlements
Conflicts with other Native American groups over land
D. A migration of these peoples to the Rocky Mountains.