The discovery of gold in Transvaal contributed to the start of the Anglo-Boer War. Option A is correct.
The first Boer War of 1880-1881 has also been known as the Transvaal Rebellion, as the Boers of the Transvaal revolted against the British annexation of 1877.
The Transvaal gold fields stemmed from gold discoveries during the 19th century in the South African Republic. The first discovery of gold in the region is recorded as being in 1852.