I believe that Makhaya suffered under the South African apartheid system because she fleed South Africa as a refugee to Botswana where she was treated much better. She would have been discriminated against in South Africa because of her skin color and not been allowed to advance in society or work.
The correct answer is who because whom should be used as the direct object of a verb or preposition. Also you can try the trick where you replace the blank with he or she. if it makes sense then you use whom. If not then you use who.
I would guess to keep the beverage fresh or the beverage contained in the bottle.