放在句首时是Look forward to sth.还是Looking forward to sth.

放在句首时是Look forward to sth.还是Looking forward to sth. look forward to do/ 还是 doing sth look forward to (doing )sth look forward to (doing) sth. 有look forward to sth. look forward to doing sth,那要是在look后加上ing后还是doing look forward to doing sth和look forward to do sth的区别? look forward to是否等于expect to so sth 有没有look forward sb to do sth 在商务信函中.结尾用Looking forward to >.这样可以吗?还是用Look forward to >. look forward to doing和looking forward to do 1,look forward to doing sth.2,hope to do sth