Half an hour has passed since the train left请问,为什么要用现在完成时,想说明什么?

After lunch ,he has a r_______for half an hour a half hour还是half an hour? 是half hour还是half an hour? half an hour or a half hour? half an hour later half an hour造句 Half an hour. The film has been on for half an hour.（改为同义句）It----half an hour ------the film--------。 The film has been on for half an hour.（改为同义句）It----half an hour ------the film--------. The film has been on since half an hour ago.（对划线部分since half an hour ago提问） The meeting has been on for half an hour.(划线部分提问,划for half an hour She has waited for Daniel for half an hour?（对for half an hour提问）（19：35之前~） half hour =half an hour half hour half an hour 的意思有和区别? an hour and half还是an hour and a half half an hour or hour中文 after half an hour.是什么意思 half an hour? 什么意思? Half an hour =什么?