Of course - happy to help out, Zach. I am guessing you are interested in hashing out how this argument is working.
I often find the best method for working through an argument - especially one I don't understand - is to work it out sentence by sentence. That is, if a particular sentence didn't make sense to me, I stick with that sentence rather than moving on. Doing the opposite is a sure fire way to get lost on these harder arguments.
I'd sketch out the argument as below:
Art criticism focuses on two things. However, these two things are related and cannot be otherwise.
I'd say the second sentence is the conclusion. Once I had a handle on the argument at this truly fundamental level, I'd go back and look at it in more detail filling things in where necessary to round out my understanding. That said, my presumption is that information is not important unless proven otherwise
Here, you probably want to round out what I have above a little - in particular because the reason the two things are related depends on what those two things are.
Let's take a look at the answer choices, keeping in mind that we are looking for the answer choice that shows the flaw in the argument:
(A) mistakes the argument. He is not arguing that quality is never objective - if it were, it wouldn't be an open question addressed in this argument.
(B) is irrelevant. It doesn't matter whether people agree about what is a matter of taste - that's going meta on us, discussing what people agree about what people agree!
(C) is the correct answer. If you think about it, the author is arguing that once something is not intrinsic, and is thus extrinsic, then it is a matter of taste - thus not objective, You see this especially in the last three lines of the argument. If you think about it, if the author cannot take this for granted, the argument falls apart. Therefore the author most decidedly *is* taking this for granted!
(D) is the opposite of what we want! If you picked this, you misunderstood those last three lines. The author is talking about where the value is not intrinsic.
(E) just makes the first sentence more plausible by telling us that at least some art work falls into the intrinsic value category. But we don't really care. Even if this isn't so, the argument can hold water.
I hope this helps! Please follow up with questions or comments if this question and answer are still unclear.