Question

which four elements are found in every protein? some proteins contain additional elements. phosphorus hydrogen carbon oxygen nitrogen sulfur

Explanation:

Proteins are macromolecules. The basic structure of proteins (amino - acids) contains carbon ($C$) which forms the backbone, hydrogen ($H$), oxygen ($O$) (in the carboxyl group of amino - acids), and nitrogen ($N$) (in the amino group of amino - acids). While some proteins may have additional elements like sulfur (in amino - acids like cysteine) or phosphorus (in some phosphorylated proteins), the four elements common to all proteins are carbon, hydrogen, oxygen, and nitrogen.

Answer:

Carbon, hydrogen, oxygen, nitrogen.