The U.S.defense secretary has rejected suggestions for a more limited approach emphasizing air strikes over troops on the ground.

VOA: standard.2009.09.22

We started on this topic on Tuesday, particularly emphasizing smallpox and kind of the history of vaccine development.

我们在本周二,重点讨论了天花,以及疫苗的发展历史

耶鲁公开课 - 生物医学工程探索课程节选