The best answer is C. i. and iii. only.
Here's the reasoning:
i. There are estimates indicating that a large number of cases occur in Africa each year, but the figure of 100 million may be an overestimate. However, the prevalence of malaria is indeed significant.
ii. Most malaria deaths occur in children under age 5, not primarily in adults over age 60.
iii. It is true that African nations spend billions of dollars each year in efforts to combat malaria, including prevention and treatment initiatives.
Thus, statements i and iii are accurate while ii is not.