小生又来请教各位了，请懂的人可以帮忙下，十分感激！

starchoi

为什么不能选A，有哪位大神可以帮忙解释下A不能选的原因吗，如果谢谢对老顾客和新顾客的效果不一样不会造成有写谢谢的人比没写谢谢的人收入低吗？

Ina study conducted in Pennsylvania,servers in various restaurants wrote “Thank you” on randomly selected billsbefore presenting the bills to their customers. Tips on these bills were an average of three percentage points higherthan tips on bills without the message. Therefore, if servers in Pennsylvaniaregularly wrote “Thank you” on restaurant bills, their average income from tipswould be significantly higher than it otherwise would have been.

Whichof the following is an assumption on which the argument relies?

AB

file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image001.pngfile:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image002.pngA. The “Thank you” messages wouldhave the same impact on regular patrons of a restaurant as they would onoccasional patrons of the same restaurant.

B.Regularly seeing “Thank you” written on their bills would not lead restaurantpatrons to revert to their earlier tipping habits.

C.The written “Thank you” reminds restaurant patrons that tips constitute asignificant part of the income of many food servers.

D.The rate at which people tip food servers in Pennsylvania does not vary withhow expensive a restaurant is.

E.Virtually all patrons of the Pennsylvania restaurants in the study who weregiven a bill with “Thank you” written on it left a larger tip than theyotherwise would have.