@bevans "all" introduces a sufficient condition, so what follows "all" will be our sufficient condition here (i.e. Labrador retrievers).
The other part of the sentence is our necessary condition (i.e. bark a great deal).
So this sentence would be diagrammed as follows:
L ==> BGD
The contrapositive, which is created by reversing AND negating, would be:
not BGD ==> not L
Hence, (A) is the correct answer here.
For a more in-depth discussion of all the Sufficient & Necessary keyword indicators and the rules associated with them, please make sure you watch our lesson on Sufficient & Necessary conditions.
Sufficient & Necessary is by far the most commonly tested form of reasoning on the LSAT, so you want to know these concepts like the back of your hand.
Hope this helps! Please let us know if you have any other questions.
