I never think myself a stupid boy. ______, I know I’m on the road to success.

A．On the other hand

B．In other words

C．On the contrary

D．By the way

对于C50-8.83/0.118型抽气凝汽式机组，分产供热的锅炉效率和管道效率分别为0.75和0.96，联产供热的锅炉效率和管道效率分别为0.90和0.98，热网效率为0.97，热化供热量为442GJ/h，则集中供热的全年节约标煤量为（）t标煤/a。

A．10 565

B．11 229

C．12 868

D．13 096