Whatisayawn(哈欠)andwhydopeopleyawn?Ayawnisoftenassociate...
问题详情：Whatisayawn(哈欠)andwhydopeopleyawn?Ayawnisoftenassociatedwithapersonbeingtired.__1__Peopleyawnformanyreasonsincludingstress,boredom,emotionandoverwork.Haveyounoticedthatyawningseemstobecontag...