Which of the following describes a curtain wall?

A curtain wall is indeed best described as a nonbearing exterior wall attached to the outside of a building. This type of wall does not support any of the building's structural weight, which is instead carried by the frame of the building itself. The primary purpose of a curtain wall is to protect the building from weather while also allowing for natural light and aesthetic flexibility.

These walls are typically made of materials like glass, metal, or other lightweight materials. They enhance the architectural design and provide insulation but do not offer structural support in terms of load-bearing capacity. This characteristic differentiates curtain walls from other types of walls, such as fire-rated enclosures or internal walls that do provide structural support.

In contrast, fire-rated enclosures for stairwells serve specific safety functions during emergencies and are designed to contain fires and smoke. Internal walls that extend to the floor above are often load-bearing and help to support the building's structure. Support structures for floors are integral to the overall architecture and carry the weight of the floors above them. This is why the identification of a curtain wall focuses on its nonbearing nature and connection to the building's exterior.