Hi there
It's good that you were able to narrow down the answers to A and C, which are the two most likely choices. Remember that, with the MCAT, you need to be able to see a 50/50 chance of being correct as success.
If the person the last paragraph of the passage is taking about is 'foreign' to us yet is conforming to a culture, then it must be their own culture (or some culture other than ours), which is why A is the best answer.
Also remember, with verbal, it is very rare that an answer will be obviously correct. You are usually looking for the 'best answer', and more specifically, the best answer according to the author's views. Context is very important.
Page 381 of the EK 1001 VR gives a more detailed explanation by the author of the questions as to why A is more correct than C, I suggest you look it over and hopefully that will help also.
Thanks for your question.