Question

21 which of the following is an example of a compound? a oxygen (o2) b gold (au) c hydrogen (h2) d water (h2o)

Explanation:

A compound is a substance made up of two or more different elements chemically combined. Oxygen ($O_2$), gold (Au), and hydrogen ($H_2$) are elements. Water ($H_2O$) is made of hydrogen and oxygen elements chemically bonded.

Answer:

D. Water (H2O)