Answer:
Explanation:
We are given four sets of relations as

A function is a relation in which every element in the first set has a unique image in the second set.
Let us check this aspect to A.
This is a function
Now come to B. 3 has two images 4 and 6. so not a function
Next is C. in C 1 has two images 0 and 6. So not a function
For D, 3 has 4 images so not a function.