If X = {1, 2, 3, 4,}, then a one-one onto mapping f: X → X such that f(1) = 1, f(2) ≠ 2 and f(4) ≠ 4 is given by
{(1, 1), (2, 3), (3, 4), (4, 2)}
{(1, 1), (2, 4), (3, 1), (4, 2)}
{(1, 2), (2, 4), (3, 2), (4, 3)}
none of these
f in (a) is clearly one-one and onto also satisfies f(1) = 1, f(2) =3 ≠2 and f(4) =2≠ 4 .