The most common frogs heard singing now are chorus frogs, tree frogs, and leopard frogs.
(The most common frogs; heard; singing now) Context(The most common frogs heard,List([0, 27))):(The most common frogs; heard singing; T:now)
The most common frogs heard,List([0, 27))
The most common frogs The most common frogs
heard heard singing
singing now
T:now