Does the mapping diagram represent a function? Why or why not?

x -7 -1 8
y -4 4

A. No; the input values x = -7 and x= -1 are paired with the same output value.
B. No; each input pairs with only one output. C. No; the output value y = -4 pairs with two different input values.
D. Yes; each input pairs with only one output.​