请各路高手解答~

coffeeqoo

Critics of sales seminars run by outside consultants point out that since 1987, revenues of vacuum cleaner companies whose employees attended consultant-led seminars were lower than revenues of vacuum cleaner companies whose employees did not attend such seminars. The critics charge that for vacuum cleaner companies, the sales seminars are ill conceived and a waste of money.
Which of the following, if true, is the most effective challenge to the critics of sales seminars?
(A) Those vacuum cleaner companies whose sales were highest prior to 1987 are the only companies that did not send employees to the seminars.
(B) Vacuum cleaner companies that have sent employees to sales seminars since 1987 experienced a greater drop in sales than they had prior to 1987.
(C) The cost of vacuum cleaner sales seminars run by outside consultants has risen dramatically since 1987.
(D) The poor design of vacuum cleaner sales seminars is not the only reason for their ineffectiveness.
(E) Since 1987, sales of vacuum cleaners have risen twenty percent.
答案是A，不知道为什么~

reebe

同问，BCDE为什么错很明显，但是不清楚A对在哪里，希望大牛帮忙解答...

yussy

说下我的看法。。
premise：Critics of sales seminars run by outside consultants point out that since 1987, revenues of vacuum cleaner companies whose employees attended consultant-led seminars were lower than revenues of vacuum cleaner companies whose employees did not attend such seminars.
conclusion：The critics charge that for vacuum cleaner companies, the sales seminars are ill conceived and a waste of money.

要想从premise推出conclusion 暗含了一个assumption 就是是seminar 导致的revenue的低
A的意思就是那些没有送员工去seminar的公司在1987年之前也是收益高的，这就说明收益高低其实和revenue没啥关系