Which of the following best describes the building blocks that make up proteins?

A. four different kinds of nucleotides connected through phosphodiester bonds
B. 20 different kinds of amino acids linked through peptide bonds
C. a variety of phospholipids that self assemble into large membrane-like structures
D. linear hydrocarbon chains with single or double carbon-carbon bonds
E. a diverse set of monosaccharides connected through glycosidic bonds