请各路高手解答~

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