现在完成时跟一段时间连用时，谓语动词要用延续性动词。常用的短暂性动词和延续性动词有：
begintostudy----study
catchacold---haveacold
borrow----keep
buy-----have
begin-----beon
close----beclosed
open------beopen
comeback------beback
die------bedead
end------beover
fallill-----beill
leave----beawayfrom
puton------bein
join------bein(beamemberof)
getup------beup;
goout------beout;
gothere------bethere;
gotobed------beinbed
arrivein–bein
getmarried–bemarried