Hi dubeyvani,
Many Schools/Programs accept both the GMAT and the GRE as part of the application process - however, not all Programs do. If you know the specific Programs that you plan to apply to, then it would make sense to research them individually (to make sure that you're taking the proper Exam to apply). The Admissions Departments at each Program would likely be happy to answer any questions that you have - so you might consider reaching out directly (they might even tell you if the Schools 'prefers' one Test to the other).
1) Have you been studying for either the GMAT or GRE (and if so, then for how long?)?
2) When are you planning to apply to Business School?
3) Which Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich