Which of the following signifies a split-level house?

A split-level house is characterized by a design that features staggered floor levels, allowing for different levels of living space that are typically connected by short flights of stairs. This layout creates a distinct separation between different areas of the home, such as the living space, bedrooms, and basement, while also maximizing the use of vertical space.

In the context of the question, Abby's house represents this architectural style, signifying its unique layout and multi-level design. The attributes of a split-level home make it a practical choice for maximizing square footage in a limited footprint, serving to separate zones for privacy while still maintaining an open feel. Therefore, understanding architectural styles helps in recognizing the distinct characteristics that define a split-level home, and in this case, Abby's house embodies those traits effectively.