Q: What forms the changing shapes of sand dunes?


Read this paragraph and choose the correct option from the provided answers:

Since we can observe wind forming sand dunes with these patterns now, we have a good explanation for how the Navajo sandstone formed. The Navajo sandstone is a rock formed from ancient sand dunes. The rock shows that the ancient wind direction changed from time to time.

 Choices:

- temperature

- humidity

- magnetism

- wind


A:
wind