Concept:The first State President of the Republic of South Africa was the politician who took office when the country became a republic.
Explanation:South Africa became a republic on 31 May 1961.
Charles Robberts Swart had been the last Governor-General.
He was then sworn in as the first State President of the new republic.
Under the republican constitution, the State President was elected by Parliament for a seven-year term.
The title was not new in South African history, but Swart was the first to hold it as head of state of the Republic of South Africa.
The other names listed were not the first State President.
Nelson Mandela and Thabo Mbeki became presidents much later under the new democratic dispensation.
Theophilus Ebenhaezer Dönges was elected but never took office due to illness.
Answer:Charles Robberts Swart
Therefore, the correct option is A.