The correct answer for the largest delta in the world is option 1, Sunderbans. A delta is a landform created at the mouth of a river where it meets a body of water, typically the ocean or a large lake. Sunderbans is located in the Indian state of West Bengal and Bangladesh and is formed by the Ganges, Brahmaputra, and Meghna rivers. It is the largest delta in terms of area, covering approximately 10,000 square kilometers.

Option 2, Amazon Basin, is incorrect as the Amazon River forms a large estuary rather than a delta. An estuary is a partially enclosed coastal body of water where freshwater from a river mixes with saltwater from the ocean.

Option 3, Greenland, and option 4, Congo Basin, are not deltas. Greenland is an autonomous territory within the Kingdom of Denmark and is known for its large ice sheet. The Congo Basin is a vast tropical rainforest in Africa.