Which set of ordered pairs does not represent a function?

a. {(-9, -3), (-4, -2), (-1, -1), (-1, 1)}

b. the set of the ordered pairs eight comma negative three, five comma negative one, two comma one, and negative one comma three.

c. the set of the ordered pairs thirty-three comma twenty-two, twenty-two comma eleven, eleven comma zero, and negative eleven comma negative twenty-two.

d. the set of the ordered pairs fifteen comma five, twenty comma four, twenty-five comma three, and thirty comma two.