On Monday,Washington,D.C., health officials reported shocking information about H.I.V.

VOA: special.2009.03.20

And one thing I want to tell you to start out with is something about this c h 3 group here.

有一点需要告诉大家的是,从这个一个碳原子和三个氢原子的组合开始。

麻省理工公开课 - 化学原理课程节选