拉矫机所要克服的阻力有铸坯在结晶器中的阻力，在二次冷却段的阻力、矫直区和切割设备形成的阻力。

I always look _____ those who never look _____ others, even though they have achieved great achievements. 

A．down on; up to

B．down upon; up to

C．forward to; down on

D．up to; down on