A delta is formed by deposition of sediment at the mouth of a river by water fanning out.
Rivers provide a water supply.
A delta is formed by deposition of sediment at the mouth of a water supply fanning out.
What is formed by deposition of sediment at the mouth of a water supply fanning out?

(a) a hurricane
(b) soils
(c) a delta
(d) an ocean
(e) soft soil
(f) an island
(g) detritus
(h) spring