Anchor: Typically an FGD retrofit can use an existing chimney or stack.
Entailed: Fdg can use an existing chimney 
Contradiction: Fdg needs a brand new chimney 
Contradiction: Surfaces are pure and real.
Contradiction: I have trouble thinking we'll solve too much of the problem. 
Contradiction: The boy is indoors.
Contradiction: The two athletes are playing a game.