What is the term for a large area of land that lacks trees?

The correct answer is plain. A plain is typically a large area of flat land that often features minimal vegetation, including trees. While plains are primarily characterized by their flat topography, they can also include grasslands and a variety of other plant types. This lack of trees is what distinguishes it from other landforms like valleys or plateaus, which may have varying elevations and different types of vegetation.

Deserts, while lacking trees as well, are generally defined by their very low precipitation and extreme dry conditions, which is a different characteristic compared to the broader definition of a plain. Thus, while both plains and deserts might be treeless, a plain specifically refers to the flat, expansive landform that can support other types of vegetation, unlike a desert that primarily represents arid land.