I studied so HARD and got a C?

I literally studied for hours, following the revision sheet word for word. when i look back on my test i want to hang myself, all of the question i know, yet i still flunked the test. i'm shattered. the worst thing is that i told my parents that i thought i did well. they are expecting an A from me.... not a C. What do i do? how can i study well? all of my other exams are the same. hours and hours of study for a **** mark.