I am not Niu Niu, but I'll give it a try. It is kind of a tough question. To negate E: Going dormant does not benefit amaryllis plants in their native habitat in some way other than simply preventing death during overly dry period. If this is true, look at conclusion, when why do we have to withdraw water to make the plants dormant, because to make it dormant does not offer any benefit, the necessary condition in the conclusion has been weakened, therefore E is the right answer. If the conclusion contains a condition, to weaken a conclusion, either find an alternative sufficient condition, or to show the necessary condition does not have to happen for sufficient condition to happen. Hope it helps. | 
