Dean swims for $72$ minutes. To keep his mind active, he works out the fraction of the total time that has passed every 30 seconds to $72$ minutes. How many of the results of his calculations can be expressed in the form $\frac{1}{n}$, where $n$ is an integer greater than $1$? 
选项为:A:$$12$$  B:$$13$$  C:$$14$$  D:$$15$$  E:$$16$$  请回答其中一个选项.