（2021 Selective Question \#7）Amrita has a bag of 36 marbles. Some are blue, some are red and the rest are yellow. There are 16 blue marbles in the bag. If she takes out a marble without looking, the probability that it is red is $\dfrac{1}{2}$. How many yellow marbles are in the bag? 
选项为:A:$$2$$  B:$$4$$  C:$$8$$  D:$$12$$  E:$$18$$  请回答其中一个选项.