We are given a statement: "All labrador retrievers bark a great deal." In order to identify sufficient and necessary conditions, sometimes it helps to rephrase it as an if/then statement.
If it is a labrador, then it barks a great deal. L - - - - - - - -> BGD suf nec
This is how that statement is diagrammed. However, this is not listed among our answer choices. Fortunately, we can create a contrapositive, which carries the exact same logic. When the necessary condition fails, then so does the sufficient condition. From this we make the contrapositive.
If it does not bark a great deal, then what can we conclude? That it is not a labrador. All labradors bark a great deal, no exceptions.
