Certain Mushrooms Tend to Appear Suddenly in Circles on Lawns

Certain mushrooms tend to appear suddenly in circles on lawns. Which of the following might be an appropriate scientific hypothesis about this.

A) Mushrooms grow only in association with grass.
B) Mushrooms grow only in the summer time.
C) The circle shape is random, even though it's almost always how these mushrooms are oriented on the lawn.
D) Mushrooms mostly grow underground from a central root structure.
E) There are some things too odd to try to explain scientifically. There's no way to know.