Based on the standard free energies of formation, which of the following reactions represent a feasible way to synthesize the product?

A. 2C(s)+H2(g)?C2H2(g); ?G?f=209.2 kJ/mol
B. C(s)+O2(g)?CO2(g); ?G?f=?394.4 kJ/mol
C. 2C(s)+2H2(g)?C2H4(g); ?G?f=68.20 kJ/mol
D. 2SO(g)+O2(g)?2SO2(g); ?G?f=?600.4 kJ/mol