关于once 的用法 一但..就..

once做一旦,就,的意思的时候,是连词,不是介词,所以不能跟上动词的ing形式conj.一旦…就…Once you begin, you must continue.一旦开了头, 你就应当继续下去. 句子应该是： the samples can be...onceD.J.[wʌns]K.K.[wʌns]adv.一次I have been there once.我到过那儿一次。曾经, 昔时I once went around the world.过去我周游过全球。 conj.一旦…就…Once you begin, you must continue.一旦开了头, 你就应当继续下去。can be sent是可以发出will be sent是将发出 看你想表达哪个意思都用sent好象重复了不好啊the tracking number will begiven to you after the samples sent