A.2.3 B.6.3 C.7.1 D.8.3
A.CO2-3>S2->C2O2-4 B.S2->C2O2-4>CO2-3 C.S2->CO2-3>C2O2- D.CO2-3>C2O2->S2-
A.F->CN->HCOO- B.CN->HCOO->F- C.CN->F->HCOO- D.HCOO->F->CN-