Which of the following correspondences can not be called a function ?
`f(x)=x^3;{-1,0,1}vec{-1,0,1,2,3}`
`f(x)=+-sqrt(x);{0,1,4}vec{-2,-1,0,1,2}`
`f(x)=sqrt(x);{0,1,4}vec{-2,-1,0,1,2}`
`f(x)=-sqrt(x);{0,1,4}vec(-2,0,1,2}`

Explanation

(i) `f(x)` in (C) and (D) are functions as definition of function is satisfied. While in case of (A) the given relation is not a function, as `f(-1)!in` 2nd set. Hence definition of function is not satisfied. While in case of (B), the given relation is not a function as `f(1)=+-1` and `f(4)=+-2` i.e. element 1 as well as 4 in 1st set is related with two elements of 2nd set. Hence definition of function is not satisfied.
(ii) B and D. In (A) one element of domain has no image, while in (C) one element of 1st set has two images in 2nd set