ANC (African National Congress) is the correct answer.

Explanation:
The struggle against apartheid refers to the fight against the institutionalized racial segregation and discrimination that was practiced in South Africa from 1948 to 1994. During this period, the majority Black African population was subjected to various forms of oppression and denied basic human rights by the white minority government.

The African National Congress (ANC) was at the forefront of this struggle against apartheid. Here is a detailed explanation of why ANC led the struggle against apartheid:

1. Formation and Early Activism:
- The ANC was founded in 1912 and initially focused on advocating for the rights and equality of Black Africans.
- In the early years, ANC leaders such as Pixley ka Isaka Seme and John Dube emphasized nonviolent resistance, education, and legal challenges to racial discrimination.

2. Defiance Campaign and Mandela's Leadership:
- In the 1950s, the ANC launched the Defiance Campaign, which involved mass civil disobedience and protests against unjust laws. Nelson Mandela emerged as a prominent leader during this period.
- Mandela's leadership and his commitment to nonviolent resistance played a significant role in mobilizing people and raising international awareness about the apartheid regime.

3. Armed Struggle and International Support:
- As the apartheid government intensified its repression, the ANC shifted its strategy to include armed resistance.
- The ANC established Umkhonto we Sizwe (MK), its armed wing, in 1961. MK carried out acts of sabotage and targeted the symbols of apartheid.
- The ANC also sought international support, and many countries and organizations, including the United Nations, imposed sanctions and boycotts against South Africa.

4. Mass Mobilization and United Front:
- The ANC, along with other anti-apartheid organizations like the South African Communist Party (SACP) and the Congress of South African Trade Unions (COSATU), formed a united front against apartheid.
- ANC-led campaigns, such as the Mass Democratic Movement and the United Democratic Front, mobilized millions of people across racial and social lines to protest against apartheid policies.

5. Negotiations and Transition:
- In the late 1980s and early 1990s, the ANC engaged in negotiations with the apartheid government to bring about a peaceful transition to democracy.
- Nelson Mandela, who had been imprisoned for 27 years, played a crucial role in these negotiations and eventually became the first democratically elected President of South Africa in 1994.

In summary, the ANC emerged as the leading organization in the struggle against apartheid due to its long history, commitment to nonviolent resistance, armed struggle when necessary, mass mobilization, and international support. Its efforts, along with those of other anti-apartheid organizations and individuals, eventually led to the dismantling of apartheid and the establishment of a democratic South Africa.