The most accurate response comparing the role of monumental architecture in the Aztec and Inca capitals is:
Both monumental structures were built in capital cities as places to worship; the Aztec structure was a pyramid that signified two gods, whereas the Inca structure was rounded and signified one god.
This statement correctly captures the essence of both civilizations' monumental architecture and their religious significance. The Aztec capital, Tenochtitlan, featured the Templo Mayor, which had temples dedicated to two primary deities (Huitzilopochtli and Tlaloc), and the Inca capital, Cusco, had the Coricancha, which was dedicated to the sun god Inti, among others.