If Names Are Purely Referential and Do Not Have Descriptive

Multiple Choice

If names are purely referential and do not have descriptive content, then 'Fido' means Fido. If names do have descriptive content, then 'Fido' means my idea of Fido. But Fido does not mean my idea of Fido. Names are purely referential. So, 'Fido' means Fido.
-Working backward from the conclusion of this argument, which of the following is the most likely justification of the last step of the derivation?

A) MP
B) MT
C) DS
D) Add
E) Simp