Question

Proteins have a 'backbone' of repeating elements, based on the similar composition of amino acids. The repeating elements of a polypeptide backbone are:
A. S-C-C-S-C-C...
B. N-C-C-N-C-C...
C. N-C-O-N-C-O...
D. C-O-O-C-O-O...
E. C-P-C-C-P-C...