Final answer:
Zinc (option A) is alloyed with copper to form brass, an alloy known for its malleability and acoustic properties, making it suitable for musical instruments.
Step-by-step explanation:
The element alloyed with copper to form brass is zinc. Alloys are mixtures composed of two or more elements, with at least one being a metal. Brass, specifically, is an alloy that combines copper and zinc to provide material properties that are superior to pure copper, such as improved malleability and acoustic properties that make it ideal for musical instruments like trumpets and trombones.
While bronze, another copper alloy, includes tin. Therefore, the correct answer to the question is 'a. Zinc'.