--When's your birthday?--It's on the 23rd of March.--Oh,____comeing soon.

问题描述:

--When's your birthday?--It's on the 23rd of March.--Oh,____comeing soon.
以上关于语法,要写为什么!

用it's
根据前面的题目可知,用的是单数形式.而it在这里是作主语,具体指代前面的your birthday