During the ___________ period, the Pueblo sites were abandoned and building styles evolved.

The correct choice is the Rio Grande Classic period, which is characterized by significant changes among Pueblo communities in New Mexico. This era, approximately from 1300 to the late 1500s, saw the abandonment of earlier Pueblo sites as populations increasingly migrated and adapted to the changing environmental and social conditions.

During the Rio Grande Classic, Pueblo building styles evolved dramatically, influenced by increased social complexity and external cultural exchanges. Architectural designs became more sophisticated, and there was a shift towards larger, multi-storied adobe structures, particularly in areas along the Rio Grande river. This period marks a crucial transition in the Puebloan way of life, indicating not only changes in building techniques but also adaptations to their social and economic surroundings.

The other options reflect different contexts or periods in Pueblo history that do not align with the mass abandonment of sites and architectural evolution seen specifically during the Rio Grande Classic.