The disease model,the optimum level is the zero: let's just be Ok; let's just not hurt.

对疾病模型而言，最优水平是零：,我们都平平安安，别受伤就好了。

哈佛公开课 - 幸福课课程节选

Now we can think about the fourth period, and the fourth period is where we start to run into some exceptions, so this is where things get a teeny bit more complicated, but you just need to remember the exceptions and then you should be OK, no matter what you're asked to write.

现在我们可以考虑第四周期，而且在第四周期,我们会遇上一些特例，所以事情有,一点复杂，但是你只需要记住,这些特例然后就没有问题了，无论你被要求写什么。

麻省理工公开课 - 化学原理课程节选