Of the following commonly used materials, the one that is not an alloy is A. Steel B. Brass C. Bronze D. Copper

The correct answer is D. Copper.

A. Steel is an alloy of iron and carbon.
B. Brass is an alloy of copper and zinc.
C. Bronze is an alloy of copper and tin.

Copper is a chemical element with the symbol Cu and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. Copper is one of the most widely used metals, and is a major component of many alloys, including brass and bronze.