Which is least for an element

Let f:A->A be an invertible function where A= {1,2,3,4,5,6} The number of these functions in which at least three elements have self image is

Let f:A->A be an invertible function where A= {1,2,3,4,5,6} The number of these functions in which at least three elements have self image is

Let f:A rarr A be an invertible function where A={1,2,3,4,5,6} The number of these functions in which at least three elements have self image is

Which one of the following is least reactive element? F Cl Br I

Which element is least electropositive?

Which of the following is the least reactive element ?

Which of the following elements is the least electronegative?