因為是過去完成進行時

例句：She had been worrying ever since the letter arrived。



　　ever since adv. (從句用過去式,主句用完成時)。

　　1、從那時到現在; 自從;自…以後;從…起。

　　2、迄今,從那時起(一直),直至今日,自那時以來,此後一直。



　　3、自…以來;一直到今。

　　例句:

　　1、He's been there ever since you left!

　　自從你離開後他就一直在那裡!

　　2、I simply gave in to him, and I've regretted it ever since

　　我就向他屈服了，從那以後我一直後悔。

　　3、I've had the hots for him ever since he came to college.

　　自從他來上大學後，我就對他春心萌動。

　　4、The girl has grown prettier than ever since I saw her a year ago.

　　一年不見，小姑娘出落得更漂亮了

是現在完成時的標誌。決定謂語動詞的形式 現在完成時