There is an argument here. The conclusion is that some announcements will inevitably turn out not to be important. Two premises supposedly support this conclusion:
Premise: Any announcement authorized by the head of the department is important.
You can diagram this: AHD ==> I
[if authorized by head of department, then important]
Premise: Announcements are sometimes issued, without authorization, by people other than the head of the department.
Notice how absolutely nothing is said about whether such unauthorized announcements might also be important.
The conclusion reflects a common error in reasoning--remember, you can't just reverse. The conclusion does just that--it assumes that if an announcement is NOT authorized by the head of department, it is not important.
Answer choice (D) is a classic, long-winded, convoluted LSAT way of saying this. Let's break down the language of the answer choice: "assumes without warrant" [assumes] "that just because satisfying a given condition is enough to ensure an announcement's importance" [that just because an announcement is made by the head of department, this is sufficient to ensure the announcement is important], "satisfying that condition is necessary for its importance" [for any announcement to be important, it must come from the head of department].
Hope this helps! Please let us know if you have any additional questions.
