Input (grade 13): Postclassic Era 900 1697 CE Collapse of many of the great nations and cities of the Classic Era, although some continue, such as in Oaxaca, Cholula, and the Maya of Yucatán, such as at Chichen Itza and Uxmal.
Output (grade 12): Many of the great nations and cities of the Classic Era collapsed, but some continue, such as in Oaxaca, Cholula, and the Maya of Yucatán, such as at Chichen Itza and Uxmal.