No flaw. If every modern office tower has climate-control yet some office buildings don’t have it, then it follows that some office buildings are not modern office towers.

No flaw. If all municipal hospital buildings are massive, and at least some of them are not forbidding, then it follows that massive buildings don’t always have forbidding appearances.

This provides information about two subgroups and assumes that those groups must overlap. It’s possible that the few disproportionate buildings designed by famous architects are all non-government buildings.

Wrong flaw. This incorrectly draws a universal “all” conclusion from a partial “some” premise. Some of the poorly designed public buildings were intended for private use, but there’s no evidence that all of them were. The stimulus, however, doesn’t arrive at an “all” statement—it just assumes that two “some” statements overlap.

No flaw. This establishes that every cathedral is impressive even though some of them are not made of stone. It therefore follows that buildings don’t need to be made of stone in order to be impressive.