已知：

C(s)+1/2O₂(g) === CO(g) △H₁= -110.5 kJ·mol^-1

C(s)+O₂(g) === CO₂(g) △H₂= -393.5 kJ·mol^-1

则C(s)+CO₂(g) ===2CO(g) 的△H 为 [ ]

A．+283.5 kJ·mol^-1

B．+172.5 kJ·mol^-1

C．-172.5 kJ·mol^-1

D．-504 kJ·mol^-1