第二天她起得很早，没吃早饭 就去了学校。
③当yesterday，tomorrow用作副词或由它们构成的短语前不用介词。如：
Can you be here at eight tomorrow morning?你明早八点能在这里吗?
Were you at home yesterday evening?
你昨晚在家吗?
④在含有a，one，every，some，all等词的短语前不用介词。如：
One day the woman learned that Liszt himself Was in town．一天妇人听说李斯特本人就在镇上。
I hope to go to the moon some day．
我希望有一天去月球。
2. before, after
(1)before表示“在某时刻或某件事之前”。例如：
He must be at home before 5:00 pm．
下午五点之前他一定在家。
Check your papers carefully before handing them in. 在交卷之前，仔细检查你的试卷。
(2)after表示“在某时刻或某件事之后”。例如：
After breakfast she hurried to school。
早饭后，她匆忙上学去了。
Call me at once after you get there．
到那儿之后马上给我打电话。
She came here after me．
她在我之后来这儿。
3．by, until, fill
(1)by表示“在……之前；到……为止”。例如：
You must finish your job by six o'clock.
你必须在六点之前完成这项工作。
By the time he got here，the meeting had been over．他到这儿时，会议已结束了。