What is defined as a curtain wall?

A curtain wall is characterized as a nonbearing exterior wall that is attached to a building structure. The primary function of a curtain wall is to provide an aesthetic facade while protecting the interior from environmental elements. It does not support any structural load from the building itself, which distinguishes it from load-bearing walls or structural components.

In contrast to other types of walls, such as those that carry the weight of floors or roofs, the curtain wall's role is primarily related to weather resistance and enclosing the space, allowing for large windows and open designs without the necessity for load-bearing capability. This is why option C precisely captures the definition of a curtain wall.