Function $f$ is defined for the set of all natural number as follows:  $$f(x)=\begin{cases}\dfrac{x}{2},(\text{when }x\text{ is even}) \textbackslash\textbackslash{} x+1,(\text{when }x\text{ is odd}) \textbackslash\textbackslash{} \end{cases}$$.  For example: $$f(3)=3+1=4$$, $$f(2)=2\div 2=1$$.  What is the value of $$f(f(f(f(f(17)))))$$? 
选项为:A:$$18$$  B:$$9$$  C:$$10$$  D:$$5$$  E:$$6$$  请回答其中一个选项.