Which statement about this mapping is true?
A The mapping represents y as a function of x, because each y-value is related to exactly one x-value
B The mapping represents y as a function of x, because each x-value is related to exactly one y-value.
C The mapping does not represent y as a function of x, because 4 y-values are related to 1 x-value.
D The mapping does not represent y as a function of x, because there are more x-values than related y-values.