为什么能说it's fine today而不说Today is fine

It's fine today. fine weather it is today. 英语翻译today is fine 和it is a fine day today 还有today is a fine It is a fine day today.It ,fine It is fine today .The sky is( ) 回答it's very fine today It's a fine ( ) (date,day) today It is fine today.____ ____ ____ it is today! It is fine today.划线部分提问,划线部分fine It is a fine day today today it is a fine day.look what fine _____ it is today!