A certain box contains $$15$$ balls that are coloured red and blue (both colours on each ball), $$12$$ balls that are coloured blue and green, and $$9$$ balls that are coloured green and red. What is the smallest number of balls that must be selected to guarantee that you have at least seven balls that share a colour? 
选项为:A:$$7$$  B:$$8$$  C:$$9$$  D:$$10$$  E:$$11$$  请回答其中一个选项.