(E)
This is a tricky one. I'm not sure if a shortcut exists to solve such problems, chunjuwu, I simply try to break it down to smaller pieces and then go about solving. Moreover, it is very important never to assume any bit of information - unless it is explicitly mentioned, a fact cannot be taken for granted.
Given:
1) There were only 5 specially order shipments (because the stem says
THE five sepcially ordered...)
2) All the shipments shipped on Friday consisted only of building material. This
DOES NOT imply that building material was not shipped prior to Friday. It only says that ONLY building material was shipped on Friday.
3) Traux had 4 shipments and 3 of them were for building material. There is no information whether the fourth order was a special order or not.
Let us examine the choices:
(A) - At least one of the shipments sent to Truax Construction last week was specially ordered. - There is no information indicating the relative breakdown of Traux's orders, so this is ruled out.
(B) - At least one of last week’s specially ordered shipments did not consist of building supplies. - We're told that all the shipments on Friday consisted entirely of building supplies, but we're not told if building supplies were shipped earlier in the week as well! All this means is that no other shipment apart from building supplies was shipped on Friday.
(C) - At least one of the shipments sent to Truax Construction was not sent out on Thursday of last week. - Again, nothing indicating this is stated in the stem. It's quite possible that the fourth shipment for Traux might have been a special order and that it was sent on Thursday
(D) - At least one of the shipments that were sent out on Friday of last week was sent to Truax Construction. This is the trickiest option. We do not know what knid of shipment was shipped from Monday through Wednesday. It is quite possible that Traux's building supplies were shipped on any day before Thursday or Friday.
(E) - At least one of the shipments sent to Truax Construction last week was sent out before Friday. True: Let's say the three building material shipments for Traux were indeed shipped on Friday. Now, the fourth shipment for Traux was NOT for building material. Since NO other shipment than building material was shipped on Friday, Traux's fourth shipment must've been shipped before Friday.