Which sentence begins with an independent clause and ends with a dependent clause?

O Because it is my birthday, my mom made a cake
O AJ can run faster than anyone
O Sarah is good at math because she studies
O Besides math, I enjoy science

O Sarah is good at math because she studies.

Is this %100 correct?

Yes, the sentence "Sarah is good at math because she studies" begins with an independent clause ("Sarah is good at math") and ends with a dependent clause ("because she studies").