So that explains probably most of the confusion here and you just want to be careful when you're reading the problems that that's what you read correctly. I think 4 everyone would now get the clicker question correct.

这可能解释了大部分人的混淆之处,你们读题目的时候一定要仔细,我相信现在每个人都能回答正确了,第三激发态，n等于。

麻省理工公开课 - 化学原理课程节选