Which of these pairs of the form (x, y)

Question

could not lie on the graph of a function
of x?
F (1, 1) and (3, 1)
G (1, 1) and (2, 1)
H (1, 1) and (1, 2)
J (1, 1) and (2, 2)

Answer 1

to have a function
you cannot have 2 or more different values of y for the same x

that is, you cannot have 2 or more points on the same vertical line
(this is often called the "vertical line test" )