We cannot do anything about protons, they are buried in the nucleus, but we can add or subtract electrons.

我们不能改变质子，它们埋藏在原子核内，但是我们能够增加或减少电子。

麻省理工公开课 - 固态化学导论课程节选

You cannot just tell the computer to enhance that or can you clean that up and then magically use zoom in not only on the image but also on the reflection of the victim in someone's eyeball.

你不能直接要求计算机增强,这张图片或者修复它,然后期待计算机很神奇地放大图片,以及死者的眼珠的反光。

哈佛公开课 - 计算机科学课程节选

Okay, good. So in Gmail context most of you know, you cannot--you can delete things but most people just save or archive emails.

好，在Gmail中，大多数人都知道，你能删除邮件,但是大多数人会选择保存或者存档邮件。

哈佛公开课 - 计算机科学课程节选