What senses does μάθημα cover? I take it conveys the sense of 'course', and 'lesson', but does that also stretch to '(school) subject' (as in "I took this subject in high school")?
"Course" is a series of lessons, not a single lesson. Isn't that right? In Greek "σειρά μαθημάτων".
The other two are correct.
In Greek the word "μάθημα" can take both meanings. Course and lesson. For example:
a) Σου άρεσε το σημερινό μάθημα; = Did you like todays' lesson?
b) Ποια μαθήματα διάλεξες για αυτό το εξάμηνο; = Which courses did you choose for this semester?
I am not sure, but for my mind the translation should be "teaching", wich is marked as incorrect..