A) one-to-one & onto and so bijection.
B) not one-to-one because x=1 and x = -1 will have same f(x) value. not onto because 0 and negative numbers in the co-domain dont have pre-image. EX: -1 in co-domain need sqrt(-1) as pre-image but it is a complex number,which is not in the domain.
C) one-to-one & onto and so bijection.
D) not one-to-one because x = 1 and x = -1 will map to the same element in the co-domain. Also it is not onto because Negative numbers in the co-domain dont have any pre-image. Ex: -1 in co-domain needs a sqrt(-1.5) as its preimage which is a complex number and so not in our domain.
