If you were preparing a defined, minimal medium for an aerobic, chemolithotrophic bacterium to grow on, which of the following constituents could not be utilized and would have to be substituted in order for it to synthesize organic molecules?

a. NaCO3
b. NH4SO4
c. K2HPO4/KH2PO4
d. Fe2+ and MgCl2
e. None of the above would have to be substituted.