**Core Concept**
The question requires identification of common sites of bleeding in the nasal cavity, specifically related to the nasal mucosa. The nasal mucosa is richly supplied with blood vessels, and bleeding can occur from various areas.

**Why the Correct Answer is Right**
The correct answer involves two sites: Woodruff's plexus and Little's area. Woodruff's plexus is a vascular network located in the anterior part of the nasal septum, which can be a source of anterior epistaxis. Little's area, also known as Kiesselbach's plexus, is a vascular network located in the anterior part of the nasal septum, which is a common site of anterior epistaxis. Both areas are richly supplied with blood vessels and can be prone to bleeding.

**Why Each Wrong Option is Incorrect**
**Option A:** Woodruff's plexus is a correct site of bleeding, but the option also includes Brown area, which is not a commonly recognized site of bleeding in the nasal cavity.
**Option B:** Brown area is not a commonly recognized site of bleeding in the nasal cavity, making this option incorrect.
**Option D:** Vestibular area is not a commonly recognized site of bleeding in the nasal cavity, making this option incorrect.

**Clinical Pearl / High-Yield Fact**
It's essential to note that nasal bleeding (epistaxis) can be categorized into anterior and posterior types, with the anterior type being more common and often related to bleeding from the anterior nasal septum, including areas like Woodruff's plexus and Little's area.

**✓ Correct Answer: C. ac. Woodruff's plexus and Little's area are common sites of bleeding in the nasal cavity.**