**Core Concept**
Depression is a complex mood disorder characterized by persistent feelings of sadness, hopelessness, and loss of interest in activities. The patient's symptoms, such as depressed mood, loss of appetite, insomnia, and lack of interest in surroundings, are classic signs of major depressive disorder (MDD). The patient's history of business loss and subsequent development of depressive symptoms suggests a significant life event triggered the onset of depression.

**Why the Correct Answer is Right**
The management of depression typically involves a combination of pharmacological and non-pharmacological interventions. Selective serotonin reuptake inhibitors (SSRIs) are commonly used as first-line treatment for MDD due to their efficacy and relatively favorable side-effect profile. In this case, considering the patient's symptoms and history, an SSRI would be an appropriate choice for managing her depression.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because antidepressants like tricyclic antidepressants (TCAs) are not typically used as first-line treatment for MDD due to their side-effect profile and potential for overdose.
**Option B:** This option is incorrect because electroconvulsive therapy (ECT) is generally reserved for treatment-resistant depression or severe depression with high risk of suicide.
**Option C:** This option is incorrect because lithium is primarily used in the treatment of bipolar disorder, not unipolar depression.

**Clinical Pearl / High-Yield Fact**
When managing depression, it's essential to consider the patient's overall medical history, including any potential interactions with medications or underlying medical conditions. Additionally, a thorough assessment of the patient's risk for suicide is crucial, especially in the initial stages of treatment.

**Correct Answer: C.**