Question

Which of the following sets represents a function? {(ordered pair one comma one), (ordered pair two comma one), (ordered pair three comma one), (ordered pair four comma one)} {(ordered pair one comma one), (ordered pair one comma two), (ordered pair one comma three), (ordered pair one comma four)} {(ordered pair one comma one), (ordered pair two comma one), (ordered pair two comma one), (ordered pair three comma one)} {(ordered pair two comma one), (ordered pair two comma two), (ordered pair three comma two), (ordered pair four comma two)}