The standard oxidation$-$reduction potentials for four redox pairs are shown in the table below.

oxidantreductantE$0$'NAD$+$NADH$-0\mathrm{.}32$ VFADFADH$2-0\mathrm{.}22$ Vfumaratesuccinate$+0\mathrm{.}03$ Vubiquinoneubiquinol$+0\mathrm{.}10$ V

Answer the following questions about redox reactions involving these molecules that occur in the electron transport chain. $($Note: FADH$2=$ FADH$2$ and NAD$+=$ NAD$+$ in the dropdown menus$)$

a$.$ Which of the molecules listed in the table is the strongest reducing agent and which is the strongest oxidizing agent?

strongest reducing agent: $[$ Select $]["$NAD$+",$ "NADH", "FAD", "FADH$2",$ "fumarate", "succinate", "ubiquinone", "ubiquinol"$]$

strongest oxidizing agent: $[$ Select $]["$NAD$+",$ "NADH", "FAD", "FADH$2",$ "fumarate", "succinate", "ubiquinone", "ubiquinol"$]$

b$.$ Which molecule donates electrons to the following Complexes of the electron transport chain? Be sure to select the first molecule that is oxidized by the Complex.

Complex I: $[$ Select $]["$NAD$+",$ "NADH", "FAD", "FADH$2",$ "fumarate", "succinate", "ubiquinone", "ubiquinol"$]$

Complex II: $[$ Select $]["$NAD$+",$ "NADH", "FAD", "FADH$2",$ "fumarate", "succinate", "ubiquinone", "ubiquinol"$]$

c$.$ Which molecule accepts electrons from the following Complexes of the electron transport chain? Be sure to select the oxidized form of the last molecule that is reduced by the Complex.

Complex I: $[$ Select $]["$NAD$+",$ "NADH", "FAD", "FADH$2",$ "fumarate", "succinate", "ubiquinone", "ubiquinol"$]$

Complex II: $[$ Select $]["$NAD$+",$ "NADH", "FAD", "FADH$2",$ "fumarate", "succinate", "ubiquinone", "ubiquinol"$]$