首先，我挑选了几张很炫的背景图片。

First, I've picked really stunning backgrounds.

youdao

我买这本书是为了帮我姐妹挑选她和伴娘的花束，但现在最困难的反而是怎么从这么多漂亮的图片中做选择。

I bought it to help my sister choose her bouquet and that of her attendants, but now the hard part is choosing from so many really beautiful pictures.

youdao

Here, I've just picked a couple of the pictures that I showed you last time when we were talking about cell communication in the immune system, What happens after the vaccine is introduced into your body is that it initiates cellular events.

我挑选了,我上次给你们展示的几幅图片,当我们讨论到,免疫系统中的细胞沟通时,讲到过当人体接种疫苗之后,能够触发,细胞活动

耶鲁公开课 - 生物医学工程探索课程节选