Hardest school subect you''ve ever studied?

Physics I, because of the damn teacher. She was a peach, seriously. I remember that during an exam, there was a problem to calculate something with momentum or whatever. It consisted of three blocks (with wheels) getting pulled. The problem asked for us to calculate the speed (or something) the block in first place.

I (and a lot of other students) calculated the red, which is in FIRST PLACE. We got the problem wrong, because to the teacher, the green one was the one in first place. After we got the exam we tried explaining to her how the red one is in first place. She said we were wrong and I barely passed the subject. I got a 70, anything below that is failing.

Physics seems interesting, but with a teacher like her, I hated the subject.