I find it easiest to skip the first 2 sentences and take the contrapositive of the next sentence so you can make it all positive. Switching "if a public space is uncomfortable it is not well designed" into "if it is well designed, it is comfortable." Then, just assign the "a - b - c = a - c" logic to "well designed - comfortable - spacious interiors = well designed - spacious interiors. " This gives you D relatively easily.

@EllieBBBB I just highlight part of it when its wrong, but having the hide button back would be nice.

@CMRT Yes

If people who have a genetic predisposition to Parkinson's have the same or less iron in their diets than people without the predisposition, wouldn't that just prove that genetics is a factor and not the iron intake? I got it right because the other answers are very wrong and this ones questionable but I don't understand at all how that's a strengthener?