A More or Less Circular Ring of Mushrooms Appears in Your

A more or less circular ring of mushrooms appears in your yard, apparently overnight. The circle is several yards in diameter. The mushrooms appear to be producing spores. What is the most likely explanation for this circle of mushrooms?

A) Mushroom spores were dropped by a circling bird, thus explaining the circular shape of the group of mushrooms.
B) One mushroom in the circle reproduced sexually to make all the other mushrooms in the circle.
C) The circle represents the fungal life cycle.
D) The mushrooms are all part of the same organism, with mycelia radiating out from the location of a germinated spore.
E) The mushroom plants in the center of the circle were older and have already died or been eaten by herbivores.