1.看动词,像Been就是完成时 2.标志词,since,yet,already,twice,once等等是完成时last短语,yesterday,then,two years ago,in the past等等是一般过去.完成时不能用瞬间动词,如learn,lend,borrow等,learn改用study,lend,borrow改用have,keep.
1.看动词,像Been就是完成时 2.标志词,since,yet,already,twice,once等等是完成时last短语,yesterday,then,two years ago,in the past等等是一般过去.完成时不能用瞬间动词,如learn,lend,borrow等,learn改用study,lend,borrow改用have,keep.