The correct answer is C) carboxysomes
Carboxysomes are polyhedral inclusion bodies that contain enzyme ribulose- 1,5-bisphosphate carboxylase/oxygenase (RuBisCO). This is responsible for the fixation of carbon dioxide in cyanobacteria. Carboxysomes have evolved as a consequence of the increase in oxygen concentration in the ancient atmosphere.
Thus, carboxysomes are not energy reserves, unlike another offered answers.