You must be tired

You must be tired
A very distinguished75-year old Chinese scholar and statesman was being honored by a university inthe eastern united states.Heand his wife had just made the 21 hours flight from Beijing,and they were met at the airport bysome friends who claimed,“You must be very tired!” his response was “keyi”.
Yet his American friends were surprised andconfused by his answer.Americans in the same plane from Beijing were kept complaining after 24 hoursof continuous travel.In the airports people could hear the complaints almost everywhere:“tired!I’ve never been so tired in my life!I’ve been sitting on planes or inwaiting rooms for 24 hours andwondered if my leg could work again!My eyes are so gritty with sleep that theyfeel like the Gobi desert was in that plane!”and so forth.
1.Whatdoes the old man’s answer mean?
2.What aspects of culture result in thedifferent answers between American and Chinese?

1.“yes ,i am tired”ora little bit
2.东西文化差异,东方人比较含蓄,就是很累,也只是说可以,而老美一般很夸张,不掩饰自己的情感