Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: Two processes are involved in the formation of a sand dune. Which two processes best describe how a sand dune forms?
wind erosion then deposition
Wind and Water (or Sand accumulation and Shaping).