Question

Delta and an estuary.

Answer 1

Delta	Estuary
1. A delta is a triangular tract of sediments at the mouth of a river.	An estuary is a deep valley formed at the mouth of a river.
2. A delta is formed due to gentle slope of land where river becomes sluggish and mud develops in its channels.	When slope of the land is prominent, water swiftly joins the Sea and there develops a deep valley or an estuary at the mouth of a river.