I am on cloud nine.为什么?

I am on cloud nine.为什么? i am on cloud nice on cloud nine是怎么来的? I'M ON CLOUD I'M ON CLOUD cloud nine straighteners on cloud 英语翻译;over the moon;down in the dumps; on cloud nine; fly off the handle I am going to UK on holiday.The plane ___ London at nine o'clock.用leave 还是leave for I am going to UK on holiday.The plane ___ at nine o'clock. 用leave 还是leave for I am going to Britain on holiday.The plane ___ at nine o'clock.用leave 还是leave forI am going to Britain on holiday.The plane ___ at nine o'clock.用leave 还是leave for what am I? I live in the cloud .I look like a ( ).I am white ang I am beauti I am keen on I am on the I am on i am on fto i am working on I,am nine 对划线部分提问 （nine是划线部分）