Dear Tutor, I am a little confused about when to move a "no" or negative indicator to the left in order to apply the "negate the necessary" rule. For example, I understand that " No Cats are Dogs can be diagrammed as such Cat-->/Dog Or Dog-->/Cat. However, what if there is a No on both sides? For example, Prep Test 111 Section 3 Question 18 Answer Choice: (B) reads "No people who understand their musical roots will be in the audience if the audience will not be treated to a good show." I almost diagrammed this by moving the "no" in the sufficient condition to the necessary condition, which would have made B correct. So, if there is a "no" or negative indicator on both sides, it is best to leave it be?

The question below made me confused because I thought the conditional statement "the painters must have needed to eat the sea animals populating the waters north of Norway if they were to make the long journey to and from the islands" was a fact because there is a Sufficent Condition that triggers a Necessary Condition there for it must be true. So when I learned A was wrong, I was confused because the conditional statement created a "rule." So, I need help. How do you disprove a conditional?

THE QUESTION:

Recently discovered prehistoric rock paintings on small islands off the northern coast of Norway have archaeologists puzzled. The predominant theory about northern cave paintings was that they were largely a description of the current diets of the painters. This theory cannot be right, because the painters must have needed to eat the sea animals populating the waters north of Norway if they were to make the long journey to and from the islands, and there are no paintings that unambiguously depict such creatures.

Each of the following, if true, weakens the argument against the predominant theory about northern cave paintings EXCEPT:

A. Once on these islands, the cave painters hunted and ate land animals.

B. Parts of the cave paintings on the islands did not survive the centuries.

C. The cave paintings that were discovered on the islands depicted many land animals.

D. Those who did the cave paintings that were discovered on the islands had unusually advanced techniques of preserving meats.

E. The cave paintings on the islands were done by the original inhabitants of the islands who ate the meat of land animals