Final answer:
The Great Plains is nicknamed 'Breadbasket of the World' due to its extensive wheat farming, which contributes significantly to global food supplies. Option A is correct.
Step-by-step explanation:
The nickname given to the Great Plains because so much wheat is grown there is a) Breadbasket of the World. This area is known for its highly fertile agricultural land, which is especially conducive to growing wheat, among other crops. The soil and climate conditions across the Great Plains, particularly in states like Kansas and North Dakota, have historically supported vast wheat farming operations.
Despite the aridity closer to the Rocky Mountains that makes the land more suitable for cattle raising, grain farms flourish. The water used for irrigating wheat and other crops often comes from the continent's largest aquifer, the Ogallala Aquifer. During times like the Devastation by the Dust Bowl, practices like dry farming and overgrazing considerably impacted this region, but it continues to be an essential food-producing area, contributing significantly to not only national but also global food supplies.