5、y.20.----Howlonghaveyoubeenhere?-----Bytheendoflastmonth.21.Thatisknowntous,saidtheexpert,isthattobaccocontainsnicotineandotherharmfulproducts,soyoushouldgiveupsmoking.22.My father retired in 2008,whenhe has beendevoting his time to gardening. 23.Indoingscientificexperiments,onemustbenomoretha