Which of the following problems are a function? (ALGEBRA)

A) (-1,2), (1,1), (1,-1), (2,1), (4,2)
B) (-2,4), (-1,1), (1,1), (2,4), (3,9)

tHaNKs!!!!

A) This is NOT a function because there are 2 points at x = 1
B) This is a function because there are no 2 points with more than 1 y value at any x point