You are presented with the quiz "A delta is formed by " 

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 "erosion is responsible for wearing down exposed places and depositing sediment in level places". 

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


 

 erosion          