**Core Concept**
Cognitive-behavioral therapy (CBT) is a type of psychotherapy that focuses on identifying and changing negative thought patterns and behaviors associated with depression. By altering cognitive distortions and maladaptive behaviors, CBT aims to improve mood and overall well-being.

**Why the Correct Answer is Right**
CBT is the most commonly used psychotherapy for depression due to its evidence-based effectiveness in reducing symptoms and improving quality of life. This therapeutic approach involves identifying and challenging negative automatic thoughts, learning coping skills, and developing problem-solving techniques to manage stress and adversity. CBT typically involves a collaborative relationship between the therapist and patient, with a focus on present-oriented and action-oriented strategies.

**Why Each Wrong Option is Incorrect**
**Option A:** Pharmacotherapy is a treatment approach that involves medication, whereas CBT is a psychotherapeutic intervention.
**Option B:** Psychodynamic therapy focuses on exploring unconscious motivations and past experiences, which is not the primary goal of CBT.
**Option C:** Dialectical behavior therapy (DBT) is a type of CBT that specifically targets emotional regulation and coping skills, but it is not the most common psychotherapy used for depression.

**Clinical Pearl / High-Yield Fact**
CBT is not a "one-size-fits-all" approach, and it may be adapted to suit the individual needs of patients with depression. This flexibility makes CBT a valuable treatment option for a wide range of patients.

**Correct Answer:** C. Dialectical behavior therapy (DBT)