不解 大全-Ⅰ-18

eshopaholic

Critics of sales seminars run by outside consultants point out thatsince 1987, revenues of vacuum cleaner companies whose employees attendedconsultant-led seminars were lower than revenues of vacuum cleaner companieswhose employees did not attend such seminars. The critics charge that forvacuum cleaner companies, the sales seminars are ill conceived and a waste ofmoney.
Which of the following, if true, is themost effective challenge to the critics of sales seminars?
(A)Those vacuum cleaner companies whose sales were highest prior to 1987 are theonly companies that did not send employees to the seminars.
(B)Vacuum cleaner companies that have sent employees to sales seminars since 1987experienced a greater drop in sales than they had prior to 1987.
(C)The cost of vacuum cleaner sales seminars run by outside consultants has risendramatically since 1987.
(D)The poor design of vacuum cleaner sales seminars is not the only reason fortheir ineffectiveness.（A）
(E)Since 1987, sales of vacuum cleaners have risen twenty percent.


答案A。 不懂，请帮忙解释下。谢谢