This black and white dog is retrieving a stick from the water .
The stick the dog is retrieving was thrown by a person
This black and white dog is retrieving a stick from the water.
The stick the dog is retrieving was thrown by a person
was thrown by a personThe dog is retrieving a stick but we cannot know who or what threw it.
was thrown by a personThe dog is retrieving a stick but we can not know who or what threw it .