Culture always plays a role in shaping what we understand as natural. what does this mean?

The term "culture" is equiavlent to the term " natural." Its what we "naturally" think, thus becoming a custom that is bid by, rather than shaped from the many diverse opinions. 
This is just an opinion. Its how I see it. But I think you should take this level a big higher. Ive just shared with you some basics. 

If you have any doubts, which im sure you may, please dont hesitate to say so. :) I hoped I helped you a little. 

Answerin vivo exposure;

Ithink the answer is c hope i