Answer:
C. Nitrogen bases
Step-by-step explanation:
It has an alternating chemical phosphate and sugar backbone, making the 'sides' of the ladder. (Deoxyribose is the name of the sugar found in the backbone of DNA.) In between the two sides of this sugar-phosphate backbone are four nitrogenous bases: adenine (A), thymine (T), cytosine (C), and guanine (G).