start at once,or you will be late for...改写———— ———— start at once,you will be late for...

start at once,or you will be late for...改写———— ———— start at once,you will be late for...
start at once,or you will be late for...改写
———— ———— start at once,you will be late for...

start at once,or you will be late for...改写———— ———— start at once,you will be late for...
Start at once,or you will be late for ...（改写）
（Unless you） start at once,you will be late for ...
除非你马上开始,不然就晚了.
unless,除非,相当于if not.

——Unless—— ——you—— start at once，you will be late for。。。