什么时候用look forward to,什么时候用be looking forward to

什么时候用look forward to,什么时候用be look forward to 什么时候用look forward to,什么时候用be looking forward to look forward to后面什么时候跟to do,什么时候用doing? The day I looked forward to ------(come).为什么用came,那什么时候用look forward to doing?有look forward to do look forward to 和 expect有什么区别?什么时候用look forward to 什么时候用expect 老师随便嘀咕了一下啊 没听清楚 look forward to 的后面什么时候动词不用加ing? 急look forward to与Look forward look forward to等于 Look forward to造句 look forward to 造句 look forward to look forward to,wonder look forward to your look forward to doing. look forward to look up/look forward to we looking forward to receiving your quotation.we look forward to your early reply.什么时候look是ing的形式,什么时候不是? LOOK forward TO 还是LOOK FORWARDS TO