Grandmother made $$20$$ gingerbread cakes for her grandchildren. She decorated them with raisins and nuts. First she decorated $$15$$ cakes with raisins and then $$15$$ cakes with nuts. At least how many cakes were decorated with both raisins and nuts?　 
选项为:A:$$4$$  B:$$5$$  C:$$6$$  D:$$8$$  E:$$10$$  请回答其中一个选项.