Many schools will accept the GRE. Check first. It is not the preferred test. If your science and math grades aren’t excellent submitting a GRE has two disadvantages:
1. The GRE has no science component. Choosing it instead of the OAT gives the appearance that you are avoiding a standardized evaluation of your science knowledge.
2. Many applicants have bibbled during their college career and have some low science grades. Scoring well on those sections on the OAT is a clear indication to the admissions teams that you are able to study and learn material independently. It is a useful tool for demonstrating maturity and growth.
Whatever your decision on standardized testing, very best of luck on your applications.