Function $$f$$ is defined for the set of all natural number as follows:  $$f(n)=\begin{cases}n+5, \text{when } n \text{ is odd}\textbackslash\textbackslash{} \dfrac{n}{2}, \text{when } n \text{ is even}\end{cases}$$,  What is the sum of the digits of the odd number $$k$$ if $$f(f(f(k)))=35$$? 
选项为:A:$$8$$  B:$$9$$  C:$$10$$  D:$$12$$  E:$$15$$  请回答其中一个选项.