If the x value is repeated is is not a function. (unless it is a negative and a positive) So lets see: For A we have 3 6 9 12 no repeations so therefore It is A For B we have 2 2 3 9, 2 is repeated so therefore it is B For C we have 4 6 4 6, both 4 and 6 were repeated so therefore is is B and lastly for D we have 3 5 6 6 And 6 was repeated so therefore it is B. A)A B)B C)B D)B