一般用在求assumption型题中
取非就是说如果这个选项不成立，也就是取它的相反的意思的话，则原文的结论就不能成立。
你可以借下面的题体会一下（FeiFei逻辑 79）
Despite improvements in treatment for asthma, the death rate from this disease has doubled during the past decade from its previous rate. Two possible explanations for this increase have been offered. First, the recording of deaths due to asthma has become more widespread and accurate in the past decade than it had been previously. Second, there has been an increase in urban pollution. However, since the rate of deaths due to asthma has increased dramatically even in cities with long-standing, comprehensive medical records and with little or no urban pollution, one must instead conclude that the cause of increased deaths is the use of bronchial inhalers by asthma sufferers to relieve their symptoms.
Which one of the following is an assumption on which the argument depends?
(A) Urban pollution has not doubled in the past decade.
(B) Doctors and patients generally ignore the role of allergies in asthma.
(C) Bronchial inhalers are unsafe, even when used according to the recommended instructions.
(D) The use of bronchial inhalers aggravates other diseases that frequently occur among asthma sufferers and that often lead to fatal outcomes even when the asthma itself does not.
(E) Increased urban pollution, improved recording of asthma deaths, and the used of asthma deaths, and the use of bronchial inhalers are the only possible explanations of the increased death rate due to asthma.
