The correct answer is (a) Kalahari.
The Kalahari is a semi-arid savanna in Southern Africa. It covers an area of 900,000 square kilometers (350,000 sq mi), making it the third-largest hot desert in the world, after the Sahara and the Arabian Desert. The Kalahari is located in Botswana, Namibia, and South Africa.
The Gobi is a desert in Northern Asia. It covers an area of 1,300,000 square kilometers (500,000 sq mi), making it the fifth-largest desert in the world. The Gobi is located in Mongolia and China.
The Chihuahuan Desert is a desert in North America. It covers an area of 450,000 square kilometers (170,000 sq mi), making it the largest desert in North America. The Chihuahuan Desert is located in Mexico and the United States.
The Sahara is a desert in North Africa. It covers an area of 9,200,000 square kilometers (3,500,000 sq mi), making it the largest hot desert in the world. The Sahara is located in Algeria, Chad, Egypt, Libya, Mali, Mauritania, Morocco, Niger, Western Sahara, and Sudan.