**Core Concept**
Peritonsillar abscess (Quinsy) is a complication of tonsillitis characterized by the collection of pus in a specific location within the head and neck region. This occurs due to the accumulation of bacteria and pus behind the tonsils, which can lead to severe symptoms such as difficulty swallowing and breathing.

**Why the Correct Answer is Right**
In Quinsy, the pus collects in the peritonsillar space, which is located between the tonsillar capsule and the superior constrictor muscle of the pharynx. This space is a potential area for pus to accumulate due to its anatomical location and the presence of lymphoid tissue. The accumulation of pus in this space can lead to the formation of a peritonsillar abscess, which can cause significant morbidity if left untreated.

**Why Each Wrong Option is Incorrect**
* **Option A:** The parapharyngeal space is a different location where pus can accumulate, but it is not the primary location for Quinsy.
* **Option B:** The submandibular space is also a potential location for abscess formation, but it is not directly related to Quinsy.
* **Option D:** The retropharyngeal space is a potential location for abscess formation in children, but it is not the primary location for Quinsy.

**Clinical Pearl / High-Yield Fact**
Quinsy is a medical emergency that requires prompt treatment, including antibiotics and drainage of the abscess. It is essential to recognize the symptoms of Quinsy, such as severe sore throat, difficulty swallowing, and trismus, to provide timely treatment and prevent complications.

**Correct Answer: C. Peritonsillar space. The space between the tonsillar capsule and the superior constrictor muscle of the pharynx.**