Final answer:
The comment by the wife that indicates the nurse's teaching about the disease process and medications has been effective is option C: "It's important for him to take his medication so that the depression will not return or get worse."
Step-by-step explanation:
The comment by the wife that would indicate that the nurse's teaching about the disease process and medications has been effective is option C: "It's important for him to take his medication so that the depression will not return or get worse." This comment shows that the wife understands the importance of medication in managing depression and preventing its recurrence or worsening. It suggests that the nurse has successfully conveyed the information about the disease process and the role of medication in its treatment.