Bob sees that the license plate number of the car consists of $5$ digits: $1$, $2$, $6$, $7$, $9$. If these $5$ digits are filled in the square~$$\huge\square+\square =\square +\square $$, which number is not used?~(adapted from $$2017$$ Math kangaroo Problems, Level $$1-2$$, Question \#$$8$$) 
选项为:A:$$1$$  B:$$2$$  C:$$6$$  D:$$7$$  E:$$9$$  请回答其中一个选项.