求助GWD。。。

hukai901

Fact: Asthma, a bronchial condition, is much less common ailment than hay fever, an allergic inflammation of the nasal passages.
Fact: over 95 percent of people who have asthma also suffer from hay fever.
If the information given as facts above is true, which of the following must also be true?

A.    Hay fever is a prerequisite for the development of asthma
B.    Asthma is a prerequisite for the development of hay fever
C.    Those who have neither hay fever nor asthma comprise less than 5 percent of the total population
D.    The number of people who have both of these ailments is greater than the number of people who have only one of them
E.    The percentage of people suffering from hay fever who also have asthma is lower than 95 percent.

答案是E。但是不明白意思，我选的A。求指点！谢谢~

sdcar2010

This is a must-be-true question: inference.

Only E is true becasuse A is less common than HF.  Therefore the total number of people who have HF is bigger than that of who have A.  Then it is a simple math problem to calculate the percentages for comparison.

Two hundred people have hay fever.  One hundred people have asthma. Out of the 100 people who have asthma, 95 of them have hay fever, in other words, 95% of the people who have asthma also have hay fever.

Then out of the 200 people who have hay fever, again 95 of them have asthma.  Translation: only 47.5% of the people who have hay fever also have asthma.

Simple math.