What causes patagonia to be dry , barren and windy

Patagonia is dry because it lies in the rain shadow resulting from high mountain range of the Andes rising on the western side of this desert. The Andes block the westerly flow of moisture from the southern  pacific from reaching the inland areas thus creating the desert.

The cold Falkland current found that is found off the Atlantic coast of south America also contributes to the aridity of the area.

The Patagonia desert occupies 673, 000 square km and is the largest desert in Argentina  and 7th largest in the world by area.

iii. and iv. only is the right answer