Question

Slash-and-burn agriculture is best defined as the process of

cutting plants and setting fires to fertilize farmland for crops.
cutting steps into a hillside to make a flat surface for crops.
using ash from fires to make farmland fertile for decades.
clearing forests to make farmland fertile for generations.

Answer 1

cutting plants and setting fires to fertilize farmland for crops.

Slash-and-burn (also called swidden or shifting cultivation) involves cutting vegetation and burning it; the ash provides short-term nutrients. It's not terracing, and the fertility usually lasts only a few years, not decades or generations.