"Climate is extreme, rainfall is scanty and the people used to be nomadic herders." The above statement best describes which of the following regions?

The question describes a region with extreme climate, scarce rainfall, and a history of nomadic herding. Let's analyze each option:

(b) Central Asian Steppe: This is the correct answer. The Central Asian Steppe is characterized by a continental climate with hot summers and cold winters, limited rainfall, and vast grasslands. Historically, it has been home to nomadic pastoralists like the Mongols and Scythians who relied on herding animals (horses, sheep, goats) for their livelihood.

(a) African Savannah: While the African Savannah has a distinct dry season and supports herding, it generally receives more rainfall than the description suggests. It's also known for its diverse wildlife, not solely nomadic herders.

(c) North American Prairie: The North American Prairie experiences seasonal temperature variations and moderate rainfall. It's more suited for agriculture than solely nomadic herding, and the climate isn't as 'extreme' as described.

(d) Siberian Tundra: The Siberian Tundra is extremely cold and has permafrost, making it unsuitable for traditional herding practices. Rainfall is also relatively low, but the dominant characteristic is the cold, not scarcity of water in the same way as the steppe.

Therefore, the Central Asian Steppe best fits all the criteria mentioned in the question.