i have been to abroad once 请问这里的once 什么词性做什么成分

I have been to. I have been there,have been 是have been in还是have been to的缩写? I Have Never Been To Me 歌词 i have ___ been to Hong Kong. I have never been to me I have been used to it. I have n____ been to another country I have been to shanghai 什么时态 I have been love you to long I have been programmed to act I have been accustomed to you. I have been to… 英语作文 -----i have never been to japan ----------- (n ) have i i have been there twice为什么不是 been to? where have you been I have been to Australian 这个句where have you beenI have been to Australian i have been to bejing twice.还是 i have been beijing twice i have been to Shanghai?和i have been Shanghai?哪个对?请详解. I have to i____ that i've been there