once you arrive和once you reach都对吗?

once you arrive和once you reach都对吗? 英语翻译once you arrive at the Expo site. love you once more see you once again You only live once Time can you back once in?once I'll ring you at once when I reach Beijing.(同义转换) please write to me at once when you arrive改为同义句：please write 改错：1.When you arrive at there ,please call me at once.______ Please write to me at once when you arrive .(同义句) 英语翻译What once moved to you may arrive trades finally is the When you arrive at there, please call me at once . 这句话错误在哪