13. three children—raquel, tiara, and xing—
each own one pet. the pets are a parrot, an
iguana, and a hamster. xing does not own
the hamster.
which of the following additional pieces of
information is needed to determine who owns
the iguana?
a. tiara owns the hamster.
b. raquel does not own the hamster.
c. raquel owns the parrot.
d. xing owns the parrot.
e. tiara does not own the hamster.

So we know each children owns one pet but, we don't know which one. The equation gives us one clue, Xing does not own the hamster. However, this mean that he can either own the parrot or the hamster. 

The question is asking for an additional information. When looking closer at the choices, we can already eliminate D. It does not give us a clue to who might own the iguana; it just shows that either Tiara or Raquel can own the iguana or hamster.
This is the same with A as well. Since Xing doesn't own the hamster but Tiara does, this just means that Raquel or Xing could own the Iguana.

B and E are not the answer as well. It says that Raquel and Tiara do not own the hamsters however, this doesn't give us the clue to who owns the iguana. With answer choice B, this would mean that Raquel owns the hamster however, it is not known who owns the parrot or the iguana. This is the same with choice E.

So the answer would be C. Since Racquel owns the parrot, than it is certain that Tiara owns the hamster since there is no way that Xing owns it and therefore, the one to own the hamster would be Xing.