A. Water closets
B. Flushing pipes
C. Lavatory basins
D. Water closets, Flushing pipes and lavatory basins
The question was asked in an internship interview.
Question is from Schedule of Rates for Water Supply works in section Schedule of Rates Metric and F.B of Civil Engineering Drawing
The best I can explain: A fitting is used in pipe systems to connect straight pipe or tubing sections, adapt to different sizes or shapes and for other purposes, such as regulating (or measuring) fluid flow. “Plumbing” is generally used to describe the conveyance of water, gas, or liquid waste in domestic or commercial environments; “piping” is often used to describe the high-performance (high-pressure, high-flow, high-temperature or hazardous-material) conveyance of fluids in specialized applications. “Tubing” is sometimes used for lighter-weight piping, especially that flexible enough to be supplied in coiled form.
Fittings (especially uncommon types) require money, time, materials and tools to install, and are an important part of piping and plumbing systems. Valves are technically fittings but are usually discussed separately.