u 常见非延续性动词和延续性动词的转变
arrive in / get to / come / go to → be in
die → be dead become a →be a
borrow →keep leave →be away (from)
buy →have open →be open
join →be in /be a member of start/begin → be on
u 典型题例1：
His grandfather died 2 years ago.(√)
His grandfather has been dead for 2 years. .(√)
His grandfather has died for 2 years.(×)
