CAREFUL READING
Read the following passages carefully. Decide on the best answer and choose the corresponding letter.

     When Christopher Columbus landed in the New World, the North American continent was an area of astonishing ethnic and cultural diversity. North of the Rio Grande, which now marks the border between the United States and Mexico, has a population of over 12 million people representing approximately 400 distinct cultures, 500 languages, and a remarkable variety of political and religious institutions and physical and ethnic types. Compared to the Europeans, the Indian peoples were extraordinarily heterogeneous, and they often viewed the Europeans as just another tribe.
     These varied tribal cultures were as diversified as the land the Indians inhabited. In the high plains of the Dakotas, the Mandan developed a peaceful communal society centered around agriculture. Only a few hundred miles away, however, in northwestern Montana, the Blackfeet turned from agriculture and began to use horses, which had been introduced by the Spaniards. As skilled riders, they became hunters and fighters and developed a fierce and aggressive culture centered around the buffalo. In the eastern woodlands surrounding the Great Lakes, the Potawatomis were expert fishermen, canoe builders, and hunters. In the Northeast, the six Iroquois nations were among the most politically sophisticated people in the world, forming the famed Iroquois Confederation, which included the Senecas and the Mohawks. This confederation, with its system of checks and balances, provided a model for the United States Constitution.