求助一道Prep题，先谢过各位了！！！！！！！

kittenalways

In a study conducted in Pennsylvania
, servers in various restaurants wrote “Thank you” on randomly selected bills before presenting the bills to their customers.Tips on these bills were an average of three percentage points higher than tips on bills without the message.Therefore, if servers in Pennsylvaniaregularly wrote “Thank you” on restaurant bills, their average income from tips would be significantly higher than it otherwise would have been.
Which of the following is an assumption on which the argument relies?

A. The “Thank you” messages would have the same impact on regular patrons of a restaurant as they would on occasional patrons of the same restaurant.

B. Regularly seeing “Thank you” written on their bills would not lead restaurant patrons to revert to their earlier tipping habits.经常看到“thank you "顾客不会又回到原来的付小费习惯
C. The written “Thank you” reminds restaurant patrons that tips constitute a significant part of the income of many food servers.

D. The rate at which people tip food servers in Pennsylvania
does not vary with how expensive a restaurant is.
E. Virtually all patrons of the Pennsylvania
restaurants in the study who were given a bill with “Thank you” written on it left a larger tip than they otherwise would have.

我的问题是：E错的原因是不是 virtually all 太绝对，如果没有加这个副词是不是就可以啦？那些实验的顾客在见到“thank you” 付的比没见之前多，排除了那些参与实验的顾客原来就爱多付小费的可能

hengfengkobe

Does it matter that "virtually all of them" left larger tips than they otherwise would have? What if "60% of them left larger tips than they otherwise would have"? Wouldn't that have still resulted in larger average incomes for the servers? Yes, it would have. Since it doesn't have to be true that it was "virtually all of them", (E) is not a MUST BE TRUE, so eliminate (E).

kittenalways

嘻嘻~~~~我没仔细看题目，我还以为是看到“thank you"的人与没看到”thank you”的人比呢，谢谢你帮我指出！！
大家相互学习，共同进步嘛！！还请多多指教！

87338618

我关于E的理解：题目问的是assumption,而E说的不是一个假设，而是一个事实，在试验调查中的人看到Thankyou给的tip比没有Thankyou多了，这是题目已经承认的事实。
而且e选项是关于试验，试验应该是一次性的，而题目做出的结论是regularly "Thank you"