Fact 1: Adelta is formed by deposition of sediment at the mouth of a river by water fanning out.

Fact 2: Delta Greek symbol, looks like a triangle.

Given the two facts above, answer the question "The deposition of sediment at the mouth of a river by water fanning out is called by what name?" with the following options: 
- unidirectional
 - Sediment
 - Calcium carbonate
 - patch reefs
 - A Greek letter
 - barrel-shaped
 - swamp vegetation
 - flooding


 

     A Greek letter    