Which type of drawing would show the layout of floor space within a building?

The correct choice is a floor plan, as this type of drawing provides a detailed representation of the layout of spaces within a building. A floor plan typically outlines the arrangement of rooms, hallways, doors, and windows at a particular level of the building. It allows architects, builders, and clients to visualize the use of space and how different areas will interact with one another.

Floor plans are essential for determining the functional flow of a building's interior, making them a vital tool in the design and construction process. They can also include indications of fixed elements like kitchen and bathroom fixtures, as well as furniture placement, which further illustrates how the space is intended to be used.

In contrast, landscaping drawings focus on the external areas surrounding a building; cross-sections provide a vertical slice through the building to showcase internal structures and relationships between different levels; and mechanical drawings concentrate on the mechanical systems within the building, such as plumbing and HVAC systems. Each of these serves a different purpose and does not provide the comprehensive spatial layout found in floor plans.