The art historian's conclusion is, "we should not hesitate to use public funds to support works of art that many people find shocking."
His support? "Great work of arts have often elicited outrage when first presented" and "it is clear that art is often shocking."
This is a Strengthen with Necessary Premise so we are looking for an answer choice that (1) strengthens and (2) is necessary to the argument.
(D), "public funds should support art," clearly supports the argument.
Now let's negate to make sure that it is also necessary. The negation of (D) is "public funds should NOT support art."
Notice the negation of (D) destroys the argument because if public funds should not support art, the conclusion that "we should not hesitate to use public funds to support works of art that many people finds shocking" no longer follows.
Hope this helps! Please let us know if you have any other questions.
