@ariella the conclusion here is, "museums ought to focus more of their security on their most valuable pieces."
The support provided? "Most stolen art is sold to wealthy private collectors" and "thieves steal what their customers are most interested in buying."
This is a Strengthen with Necessary Premise question, so we are looking for the answer choice that not only strengthens but that is also necessary to the argument.
(D) states, "most museums provide the same amount of security for valuable and not-so-valuable art."
This definitely seems to strengthen since if (D) is true, the recommendation that museums ought to focus more of their security on their most valuable pieces would make sense.
However, the problem with (D) is that it is not required for the conclusion.
The negation of (D) is, "most museums do not provide the same amount of security for valuable and not-so-valuable art." This does not destroy the argument that museums ought to focus more of their security on their most valuable pieces.
Compare this with (B), "art pieces that are not very valuable are not very much in demand by wealthy private collectors."
This clearly strengthens the argument that museums out to focus more of their security on their most valuable pieces.
Now let's negate (B) to make sure it is also necessary to the argument.
The negation of (B) is "art pieces that are not very valuable are very much in demand by wealthy private collectors."
This clearly destroys the argument, so (B) would be the correct answer.
Hope this helps! Please let us know if you have any other questions.
