Many students were watching the story of the heroes from Changjiang University on TV, ________ moved to tears.

A．all of them

B．all of whom

C．all of that

D．all of which

第二次世界大战以后，电子工业和半导体工业对超纯材料的要求导致（）及各种单晶制备方法和气相沉积法的出现。