I dont know how and why student fails in exam? but i know how i fail on my exam its pretty simple because i dont study too hard..i hate reading and other thing is that i noticed in most of the  nepali student in US, i am not saying all of em but most of em dont care abt study once they get in USA in F1. I myself planned that study first then work but i am doing exactly opposite,  thats why i have C's in most of my class....