The correct answer is D. In South Africa, the nation's chief executive is chosen by the legislature.
In South Africa, the president is elected by the members of the National Assembly (the lower house of Parliament) from among its members. This means that the chief executive (the president) is not directly elected by the citizens, as is the case in Nigeria, where the president is elected by popular vote.
In Nigeria, the president is elected directly by the citizens during national elections, which is a key difference in the process of selecting the head of government between the two countries.