There are $$17$$ balls in a bag. Each ball has a number from $$1$$ to $$17$$ on it. We randomly pick a ball from the bag. What is the smallest number of balls we have to pick in order to be sure that we have at least one pair of balls with a sum equal to $$18$$? 
选项为:A:$$7$$  B:$$8$$  C:$$10$$  D:$$11$$  请回答其中一个选项.