求50句复合句+翻译,要稍微长一点的,每句超过20个单词.急啊.

1楼1．当你离开教室时,务必关灯.Be sure to turn off the lights when you leave the classroom.2．你一旦开始,就必须进行下去.Once you begin,you must go on.3．如果你不快点,你就会误了火车.You’ll miss the tra...