Adelta is formed by deposition of sediment at the mouth of a river by water fanning out, and erosion is responsible for wearing down exposed places and depositing sediment in level places. Given these facts, a delta is formed by  among the following options:
- erosion
 - motion
 - plate shifts
 - flooding
 - loose soil
 - Earthworms
 - compression
 - gravity


 

 erosion        