Question

She has been sleeping for the last four hours.
He has a prejudice over homeopathy.

Are these sentences correct?

Answer 1

She has been sleeping for the last four hours. or since 5 o clock. Use" since " to mention the starting point of time and "for "the duration of time or 
Ex i have been studying in this school for the last five years or i have been studying in this school since 2009

Prejudice over is wrong. prejudice to something is correct