Final answer:
Deserts, including the Sahara, Namib, and Kalahari, cover about 40% of Africa.
Step-by-step explanation:
Deserts cover a significant portion of Africa, with the largest being the Sahara Desert. The Sahara alone is approximately 3.6 million square miles, close to the size of the United States. When you add Africa's other deserts, like the Namib and the Kalahari in the southwest, and the desert region in the African Horn, the total coverage is substantial. Taking into account that the Sahara Desert is not the only desert in Africa, the correct answer to the question is that deserts cover about 40% of Africa (option a).