The statement that is not true is: "the Sahara is the largest desert in Africa." This is incorrect because while the Sahara is the largest hot desert in Africa, it is not the largest desert globally. The largest desert in the world is Antarctica, which is classified as a cold desert.
The other statements are true:
- The Sahara is indeed located in Africa.
- It extends into southern Africa.
- The region does stretch across about one-fourth of the African continent.
So the statement to select is: "the Sahara is the largest desert in Africa."