Increased availability and affordability of air-conditioning --> Increase in sales of houses with low ceilings and thin walls(A) High ceilings and thick walls enable houses to withstand many types of severe weather that are common in North America.
Incorrect, this has
no impact, we want an option that decreases our confidence in the cause-effect relationship, knowing how many weathers can houses withstand doesn't help on that front.
(B) Thin-walled, low-ceilinged houses are more costly to heat in winter than thick-walled, high-ceilinged houses.
Incorrect, this has
no impact, knowing costs doesn't change our confidence in the cause-effect relationship.
(C) Houses with low ceilings and thin walls were prevalent in North America even where there was no demand for residential air-conditioning.
Correct, this casts a doubt that
Increased availability and affordability of air-conditioning led to an
Increase in sales of houses with low ceilings and thin walls.(D) Thin walls allow cool, air-conditioned air to escape more readily from houses than do thick walls.
Incorrect, doesn't decrease our confidence in the cause-effect relationship. In fact, this leads us to think that thin walls houses are more favorable than thick walls during air-conditioning, somehow strengthens the conclusion.
(E) Soon after World War II, new thermal-insulating technology was widely applied in house building.
Incorrect,
no impact, this talks about another technology so doesn't affect our confidence in the cause-effect relationship.