现在完成时用法短暂性转换延续性1 转换成延续性动词如do keep have wear have a coldstart/begin to do sth. do sth.borrow keep lose not havebuy have put on wearcatch/get a cold have a coldget to know know2 be +介词begin be onbe in sw./at school/at home/on the farm3 be +形容词，副词come/go back, return be backcome/go out be outclose be closed open be openbecome beget up be up die be deadleave sw. be away from sw.fall asleep/get tot sleep be asleep
