**Core Concept**
The facial muscles play a crucial role in expressing emotions and controlling facial expressions. The muscles involved in frowning are part of the facial musculature, specifically those that contract to produce a furrowed brow. Understanding the anatomy of these muscles is essential for recognizing and reproducing various facial expressions.

**Why the Correct Answer is Right**
The corrugator supercilii and procerus muscles are responsible for frowning. The corrugator supercilii muscle originates from the medial orbital prominence and inserts into the skin of the forehead, causing the brow to furrow. The procerus muscle, on the other hand, originates from the nasal bone and inserts into the skin of the forehead, also contributing to the frowning expression. When these muscles contract simultaneously, they produce a characteristic furrowed brow.

**Why Each Wrong Option is Incorrect**
**Option A:** The zygomaticus major muscle is primarily responsible for smiling, as it elevates the angle of the mouth. It is not involved in frowning.
**Option C:** The dilator naris and depressor septi muscles are responsible for the movement and shape of the nostrils, not facial expressions.
**Option D:** The depressor anguli oris muscle is involved in lowering the angle of the mouth, but it does not contribute to frowning.

**Clinical Pearl / High-Yield Fact**
When assessing facial palsy, it is essential to examine the muscles involved in facial expressions, including those responsible for frowning. The inability to frown may indicate involvement of the facial nerve (cranial nerve VII) or other underlying conditions.

**✓ Correct Answer: B. Corrugator supercilii and procerus**