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27.   (30565-!-item-!-188;#058&005567)

Among people who experience migraine headaches, some experience what doctors call "common" migraines, whereas others experience "classical" migraines.  Siblings and spouses of common migraine sufferers are themselves twice as likely as the general population to experience common migraines.  Siblings of classical migraine sufferers are four times more likely than the general population to experience classical migraines, whereas spouses of classical migraine sufferers are no more likely than the general population to experience such headaches.

The information above provides the most support for which of the following hypotheses?

(A) Susceptibility to classical migraines is more dependent on hereditary factors than is susceptibility to common migraines.

(B) Unmarried adults are more likely to suffer from classical migraines than they are to suffer from common migraines.

(C) People who do not experience migraine headaches are unlikely to have spouses who are migraine headache sufferers.

(D) Children of people who suffer from common migraines are not more likely than the general population to experience a common migraine.

(E) Between one-quarter and one-half of the general population suffer from either common or classical migraine headaches.

另外几个都没关系，但是A是怎么推出的呢。就因为CLASS造成兄妹的概率高？题目怎么理解，求NN解答，万谢

看清楚题目的指代关系就会明白了

兄弟和夫妻易患 common migraine  是常人的2倍

兄弟易患classical migraine是常人的4倍

夫妻患classical migraine不比常人高

楼上的 这次明白了么？