Explanation

This is an inference question. We are given a series of facts and then asked to draw an inference. On inference questions, the bar is very high -> the correct answer must 100% without a doubt be true.

Comcorp Shipping Clerk: Last week, no shipments of building supplies were sent out on Friday. The five specially ordered shipments sent out last week were sent out on Thursday, and each of those specially ordered shipments consisted entirely of building supplies. Four shipments were sent to Truax Construction last week, none of which consisted of building supplies.

If the shipping clerk's statements are true, which of the following must also be true?

a. All of Comcorp's shipments of building supplies last week were specially ordered.
We know that all of the specially ordered shipments contain building supplies, but some others could have contained building supplies as well. Do not reverse the argument!

b. None of Comcorp's shipments sent on Friday of last week was sent to Truax Construction.
None of the specially ordered shipments were sent out on Friday, but we know that the shipments sent to Truax were all non-specially ordered (because they contained no building supplies). These could have been sent on any day, we have no idea.

c. None of the shipments sent by Comcorp by Truax Construction last week was specially ordered.
If all of the specially ordered shipments contained building supplies, and none of the shipments to Truax contained building supplies, then it is 100% certain that none of the shipments sent to Truax was specially ordered. Our 100% bar truth has been reached!

d. None of Comcorp's shipments sent on Thursday of last week was sent to Truax Construction.
We have no idea what day the shipments to Truax were sent. All specially ordered shipments were sent on Thursday, but we have no limit on when the non-specially ordered shipments were sent.

e. All of Comcorp's shipments of building supplies last week were sent out on Thursday.
Similar to answer choice a, it is possible that building supplies were also included in non-specially ordered shipments, and these could have been sent on another day.

Answer: C