Which relation is a function?

A- (1,-1), (-2,2), (-1,2), (1,-2)
B- (1,4), (2,3), (3,2), (4,1)
C- (4,2), (3,3), (2,4), (3,2)
D- (1,2), (2,3), (3,2), (2,1)

B- (1,4), (2,3), (3,2), (4,1)

Step-by-step explanation:

A function is a relation that pairs each element from set X (first number) to only one element of the set Y (second number)

For example let's say we have a set of X (3, 4) and a set of Y (6, 8)

The pairs would be (3,6), (4,8) now that's a function but if it were like this (3,6), (3,8) it wouldn't make a function since 3 is paired with both 6 and 8

The option that has requirements of a function is B.