How do CAM plants fix carbon?

CAM plants temporally separate carbon fixation and the Calvin cycle. Carbon dioxide diffuses into leaves during the night (when stomata are open) and is fixed into oxaloacetate by PEP carboxylase, which attaches the carbon dioxide to the three-carbon molecule PEP.

Explanation:

the answer for this question would be d. glaciers

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.