**Core Concept**
The patient's symptoms suggest a diagnosis of Major Depressive Disorder (MDD), characterized by persistent feelings of sadness, hopelessness, and loss of interest in activities. Management of MDD typically involves a combination of pharmacological and non-pharmacological interventions.

**Why the Correct Answer is Right**
The patient's symptoms have been present for more than 2 months, indicating a need for acute treatment. Selective serotonin reuptake inhibitors (SSRIs) are recommended as a first-line treatment for MDD due to their efficacy and relatively favorable side-effect profile. SSRIs work by increasing the concentration of serotonin in the synaptic cleft, thereby enhancing neurotransmission. The patient's recent loss of her husband and resulting loneliness may have triggered her depressive episode.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while benzodiazepines may provide temporary relief from anxiety symptoms, they are not an effective treatment for MDD and can exacerbate depressive symptoms in the long term.
**Option B:** This option is incorrect because while electroconvulsive therapy (ECT) can be an effective treatment for severe or treatment-resistant depression, it is typically reserved for patients who have not responded to other treatments or who are at risk of harming themselves.
**Option C:** This option is incorrect because while cognitive-behavioral therapy (CBT) is a useful adjunctive treatment for MDD, it is not sufficient as a standalone treatment for acute symptoms.

**Clinical Pearl / High-Yield Fact**
When managing patients with MDD, it's essential to assess for suicidal risk and to monitor for side effects associated with antidepressant medications, such as increased anxiety, agitation, or changes in appetite.

**Correct Answer:** C.