Which of the following is an example of a compound?

Salt is an example of a compound because it is composed of two or more different elements that are chemically combined in a fixed ratio. Specifically, table salt, or sodium chloride (NaCl), consists of sodium (Na) and chlorine (Cl), which together form a distinct substance with unique properties different from those of the individual elements. Compounds are characterized by the way their elements bond chemically, resulting in new properties and behaviors that do not resemble their constituent elements.

In contrast, the other options—oxygen, gold, and carbon—are all examples of elements. Each of these substances cannot be broken down into simpler substances by chemical means and represents a single type of atom. Therefore, they do not meet the criteria for being classified as a compound.