A Is the correct sentence.
B is incorrect because commas in list appear as: item 1, item 2, item 3, AND(comma before the and) item 4.
The fixed sentence should be: I got a tutor to help me with biology, chemistry, physics, and algebra.
C is incorrect because commas should not cut off essential information.: To help me with biology is essential information, otherwise, we would have: I got a tutor chemistry, physics, and algebra.
The fixed sentence should be: I got a tutor to help me with biology, chemistry, physics, and algebra.
