It was ________ my father worked ________ I worked now. [ ]

A. where; that

B. wherever; where

C. that; where

D. there; where

反应C（石墨）⇒C（金刚石）是吸热反应，由此可知（　　）

A．石墨比金刚石更稳定

B．金刚石和石墨可以相互转化

C．金刚石比石墨更稳定

D．金刚石和石墨不能相互转化