Prepositions are tricky little things, when you think about it. When I was min eighth grade, my English teacher has us all draw a “Preposition Mountain.” Basically, me having very limited drawing skills at the time, I had to draw a hill with little stick people all over it to illustrate the prepositions. “On the mountain,” “up the mountain,” “over the mountain,” “beneath the mountain,” etc. Before that, I don’t recall ever really thinking much about prepositions at all.
The first time I realized how tricky prepositions really were was when I tutoring ESL student at my university and one of them asked me “What does ‘at’ mean?”
Prepositions went on to be a big problem with those students, and every student I’ve had since. Think about it: the only difference between doing something kind and “cooking for your mother” and preparing meal for unknown cannibals is the little preposition “for.”
For the college students I tutored, location was the frustrating thing. After they kept saying “The bus stop on the university” I corrected them and told them it was “at.” I even drew them a picture.
The next time, they said “When we got at the bus.”
“At?” I said. “On the bus, not at the bus.”
“Teacher!” said one of the students, drawing a quick picture, “Not on, at!”