The design load is defined as:

The design load is a critical concept in construction and structural engineering, encompassing the total load a structure is designed to safely sustain. This includes various components, such as live loads (which can change over time, like people and movable furniture) and dead loads (permanent fixtures such as walls, roofs, and fixed furniture).

Specifically, defining it as the total load a structure is designed to support captures the essence of safe structural design. Designers and engineers consider all possible factors to ensure the structure can handle not just the weight of furniture but also other elements like snow, wind, and seismic activity. This ensures the building remains safe and functional under various circumstances.

Option D correctly combines two relevant aspects: living room furniture represents part of the live load, while the total load definition encompasses all loads. By acknowledging both, this choice reflects a comprehensive view of design loads as it pertains to structural integrity and safety.