2. Understanding electron donor and electron acceptor. For each reaction draw arrows for the reduction of the electron acceptor and the oxidation of the electron donor following the format of

the generic equation below: \text { a) } \mathbf{H}_{2} \mathbf{S}+\mathbf{N O}_{3}^{-} \rightarrow \mathbf{S O}_{4}^{2-}+\mathbf{N}_{2} \text { b) glucose }+\mathrm{O}_{2} \rightarrow \mathrm{H}_{2} \mathrm{O}+\mathrm{CO}_{2} \text { c) } \mathrm{H}_{2}+\mathrm{CO}_{2} \rightarrow \mathrm{CH}_{4}+\mathrm{H}^{+} \text { d) } \mathrm{SO}_{4}^{2-}+\text { lactate } \rightarrow \mathrm{H}_{2} \mathrm{~S}+\mathrm{CO}_{2}