A function is said to be a function if it is one one, i.e. for every value of x thier exists only one possible value of y
In the given question we have :
(2,5), (k,0), (-9,2),(0,-9)
So, k cannot be equal to 2,5,-9,0
because if k is equal to any of these value, then they are not one-one hence cannot form fuction
From the given option we are left with only 3
So, k = 3 which will give 0
Thus k = 3
Answer : c) k =3