A work of architecture, if it is to be both inviting and functional for public use, must be unobtrusive, taking secon...

I need a better explanation why B is correct. I know that: I and F -> not O / O-> not I or not F and that Modern architects violate the precepts (not I or not F or both). How can we conclude from that because modern architects are not I or not F (violate the precepts) that they are O? Isn't that deducing a sufficient from what is necessary? Please explain or am I just completely wrong in my method? Thank you