Mr. White works with a chemicals import export company, but he---- for this industrial fair, since he is on leave.

為何目前進行時is working可以，而目前完成時has been working不對？

因為懷特先生在休假，所以近期都在這個工業展覽會幫忙，如何不對？這個又不是只開一天。。。

Mr. White works with a chemicals import export company, but he---- for this industrial fair, since he is on leave.

為何目前進行時is working可以，而目前完成時has been working不對？

因為懷特先生在休假，所以近期都在這個工業展覽會幫忙，如何不對？這個又不是只開一天。。。

【答】since he is on leave 是緣由狀語從句，不是時間狀語從句，所以主句不可以用目前完成進行時has been working ；這里的目前進行時is working 用來表示暫時的狀況。