Ⅱ.单项选择(满分20分)21. Nowadays many young people get into ____ habit of smoking in ____ public and can't kick it.
My brother lives in ______ on ______ floor.
December is _______ month of the year.
This took place in the ______ .
It is only _____ from my home to the train station.
There are ______ in this building , I live on ______.