The correct answer is B) popular opinion turned against South Africa Apartheid.
The reason why the U.S. eventually stopped supporting South Africa was that popular opinion turned against South Africa Apartheid.
With the news reports circulating around the world, the International community paid attention to the harsh conditions of black people under the Apartheid regime in South Africa. Particularly after the Sharpeville incident of 1960, where black people that were protesting were shot by the Police. In this terrible incident, 69 people died and 186 were wounded. So the reason why the U.S. eventually stopped supporting South Africa was that popular opinion turned against South Africa Apartheid.