You are presented with the quiz "The deposition of sediment at the mouth of a river by water fanning out is called by what name?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "adelta is formed by deposition of sediment at the mouth of a river by water fanning out" and "delta Greek symbol, looks like a triangle". 

So, what's the best answer to the question?


 

     A Greek letter      