I can't know it because it just is that sign.

我们不能自然的认识符号。

耶鲁公开课 - 文学理论导论课程节选

Now in a stoplight, it only has three, one is tempted to say, variables plainly differing from each other: red, yellow and green we have two ways of thinking about the red light.

交通灯，三种灯，红黄绿，它们的颜色和彼此不能,我们有两种方式认识红灯的意思。

耶鲁公开课 - 文学理论导论课程节选

So, in terms of what it is that you need to prepare and bring with you for the exam, you need to bring your MIT ID, especially if you haven't been showing up regularly to your recitations and you aren't 100% sure if your TA knows exactly who you are, you need to make sure you have your MIT ID with you.

那么，关于你需要做哪些准备,考试可以带哪些东西，你需要带着你的学生证，尤其是如果你没有经常地参加,习题课,你不能百分之百保证,你的助教确实认识你，那么你更得确保自己到时带着学生证。

麻省理工公开课 - 化学原理课程节选