I am not surprised that you have trouble with this question. (and please ignore the rudeness above, I wonder how he would sound in your language!)
Most English speakers are familiar with a.m. - morning (anti-meridion or before noon) and p.m. - afternoon (post or after meridion)
Few would know a.p. (as prescribed) unless their doctor or pharmacist explained it.
I had to ask the pharmacist, whose office is beside my desk, what a.u. meant. She said that it meant in each ear, but needed to look it up to check.
Very difficult homework indeed.
edit: that can't be right. I reread your post and it can't mean take a pill in each ear so our pharmacist wouldn't answer your question correctly either.

Last edited by Zed; 01/16/2006 5:10 PM.