Is it ok that this author does not ever directly cite or acknowledge any perspectives? I know the earlier page on this says you can paraphrase, cite or say things like "opponents of this view....".

Can someone explain in more detail why 24 is D and not E? I debated between the two a lot but chose E. I picked E because the passage describes how the agents would go to the gossip columnists and thought of E as more of a literal answer, while D is more big picture description.

I think you're confused by thinking that because one principle is true for a member of a superset means that it is true for all members of a superset. We can't infer that all planetary systems have large comets. The Earth's planetary system is one planetary system of many. Just because something is true about the Earth's planetary system does not mean that all other planetary systems also frequently have large comets, unless it is explicitly stated as a premise.

From the stim, we know that for a planet to produce intelligent life it needs to not be struck frequently by large comets. To evaluate if the conclusion is true we need to know whether those large planets really are needed to prevent being struck by comets and thus develop intelligent life. If comets are not common in planetary systems in the first place, then we can evaluate the argument to be weak as large planets are not necessary for intelligent life. If the comets are common, then we can evaluate the argument to be strong because it shows that large planets are needed for intelligent life.

Did anyone else get thrown off by the fact it says "explanations" in D when really it seems the author is arguing for one explanation (the cause being synthetic pollutants)?

Same!! They talk about innovations that the Mexican artists made during the time period but nothing implied modern art trends to me so I thought it was wrong