Answer:
Choice D is correct answer.
Explanation:
We have given relations .
We have to choose relations which are functions.
Function f from a set X to a set Y is defined by a set G of ordered pairs (x, y) such that x ∈ X, y ∈ Y.
Function is defined as a rule that assigns each input a single output.
So, choice B and C represent a function. But choice A is not a function since a single input can't have more than 1 output.