Sometimes it's easier actually not touch it to the metal, -- I should have- TA: It's hard to see if it's moving or not.

有时候它更容易不接触金属，我本应该-,助教：很难看到它是否移动了。

麻省理工公开课 - 化学原理课程节选

All your TA's have either already have their extra office hours, or there are some that will be going on tonight or tomorrow, so keep those in mind as your finishing up your studying for the exam.

你们的助教们有的已经做过额外的答疑，而有的会在今天晚上或者明天答疑，因此在你复习准备,考试的时候不要忘了这些。

麻省理工公开课 - 化学原理课程节选