Question

which of the following is a function from { 1,2,3,4,5} to {1,2,3,4,5} that is one-to-one and onto?
a){(1,2) (2,3) (3,4) (4,5) (5,5)}
b) {(1,5) (2,4) (3,3,) (4,2) (5,1)}
c){(1,3) (2,3) (3,3) (4,3) (5,3)}