A. Inductive rather than Deductive. So, probably B has p4. Analogies of the Affinity argument. Unlike the first two arguments, the Affinity argument tells us something about the nature of the soul. The Soul is like the Forms.
Visible things have a composite nature.
In order to corrupt or change, something must have a composite nature. Forms never change, but sensible particulars do. While it is natural for the body to dissolve, by nature the soul indissoluble. When body and soul are together, it is natural for the soul to rule the body, it is the nature of the body to be ruled. It is the nature of the gods to rule as well, and they are immortal, so probably the soul is immortal as well.