The number of functions $f:\{1,2,3,4,5\} \longrightarrow\{1,2,3,4,5\}$ such that $f(f(n))=n$ for all $n \in$ $\{1,2,3,4,5\}$, is

• A

  25.
• B

  $120 .$
• Correct answer
  C

  41.
• D

  31.

Hence, the correct answer is option: 'C'.