When the number of students visiting me during office hours increases exponentially in a given week, I know that one or more of the following is true:
* The current homework assignment is more challenging than the previous homework assignments.
* The syllabus claims that there is an exam coming up soon.
* They are doing equally poorly in their other classes, and need to boost their grade in one of them---might as well be this one.
* They want to inflict their sickie germs on me. Share the wealth!