At the scene of the dig south of the capital, Elena and the other family members present were resolute in their determination to find clues as to the fate of their family members.

VOA: standard.2009.12.18

If you looked at the antibodies that were present in the blood, for example, you would find that most of those antibodies are IgM during this initial period of antibody concentration rise.

如果你现在观察血液中存在的抗体,举个例子,在初次免疫的抗体浓度上升阶段,你将会发现大部分的抗体都是IgM

耶鲁公开课 - 生物医学工程探索课程节选

And you'll use "If I were" to talk about yourself in the present in relationship to the past.

你可以用“If I were”来比较现在的你和过去的你。

If I were 课堂 - SpeakingMax英语口语达人

So, some of these cases were probably due to polio that was transmitted by incompletely killed virus that was present in the vaccine.

因此,那些病例的发病的原因,是被那些疫苗中携带的,没有被完全杀死的病毒感染

耶鲁公开课 - 生物医学工程探索课程节选