Which of the following best describes a purpose of drains in a building?

The purpose of drains in a building primarily revolves around the efficient removal of unwanted liquids from fixtures. Drains are designed to collect wastewater from various sources such as sinks, showers, and toilets, directing it away from the living space and into the appropriate sewage or wastewater systems. This function is essential for maintaining hygiene, preventing flooding, and ensuring that the building remains a safe and pleasant environment for its occupants. Drains are integral to plumbing systems, as they manage the flow of liquids, preventing accumulation and potential damage or health hazards.

Other functionalities, like distributing heating or supplying gas, do not pertain to the primary role of drains. These are specific to heating systems and gas supply lines, respectively, which focus on different aspects of a building's infrastructure. Aesthetic design also does not relate to the fundamental function of drains, as they are primarily utilitarian features within the plumbing system. Thus, the correct description emphasizes the critical role of drains in removing unwanted liquids efficiently.