请教一个逻辑假设的问题

In a study conducted in Canada, servers in various restaurants wrote “Thank you" onrandomly selectedbills before presenting the bills to their customers. lips on these billswere an average of threepercentagepointshigher than tips onbills without the message. Therefore,if servers in Canadaregularly wrote “Thank you” onrestaurant their averageincome from tipswould be significantly higher than it otherwisewould have been.

Which of the following isanassumption onwhichthe argument relies?

A.   The “Thank you"messages would have thesame impact on regular patrons ofa restaurant as they would on

occasional patrons of thesame restaurant.

B.   Regularly seeing “Thank you" written on their bills would not lead restaurant patrons to revert to their earlier tipping habits.

C.   The written“Thank you"reminds restaurant patrons that tipsconstitute a significant part of the income of many

food servers.

D.   The rate at whichpeople tipfood servers in Canada doesnotvary with howexpensive a restaurant is.

E.   Virtually allpatrons ofthe Canadian restaurants inthe study who were given a bill with “Thank you” written onit

left a larger tip thantheyotherwise would have.

我个人觉得E比B的假设更能支持结论。 因为 Virtually allpatrons 事实上所有的老客户都会with large tips 。 请大牛分享一下看法