Step 1: Historical background.
After the end of apartheid in South Africa, Nelson Mandela became the first Black President in 1994. Alongside him, two deputy presidents were sworn in: Thabo Mbeki and F.W. de Klerk.
Step 2: Analyze the options.
(A) Thabo Mbeki: Correct — Thabo Mbeki was the one who was first sworn in as second deputy president.
(B) Nelson Mandela: Incorrect — Mandela was sworn in as President, not deputy president.
(C) Zenani: Incorrect — Zenani is Mandela’s daughter, not involved in the presidential swearing-in.
(D) Mr. de Klerk: Incorrect — He was sworn in as the first deputy president, not second.
Step 3: Conclusion.
Thus, the correct answer is (A) Thabo Mbeki.