So when you go ahead and draw these on your problem-sets or on your exams, it's a good idea to put these dashed lines in, both for you and for people reading it to see exactly where your molecular orbitals are coming from.

所以当你在做课后题,或者考试的时候要画这些图时，最好把这些虚线放进去，既方便你自己也方便别人知道,这些分子轨道是从哪里来的。

麻省理工公开课 - 化学原理课程节选

We're also posting a practice exam for you to take, so after you're completely done your studying, it's good to have everything done before you take the practice exam, and then sit down just with this sheet here and your calculator, and ideally a timer, and make sure you can do the practice exam in the allotted amount of time.

我们还将给出一份模拟试题，因此在你完全复习好之后，最好先复习完,再做这份模拟试题，坐下来,只拿出这张表与计算器，最好还有个计时器，确保自己完成模拟题,在规定的时间内。

麻省理工公开课 - 化学原理课程节选