<s>[INST] context: LUDWIG'S ANGINA - Submandibular space lies between mucous membrane of the floor of mouth and tongue on one side and superficial layer of deep cervical fascia extending between the hyoid bone and mandibular on the other.it is divided into two compaments by the mylohyoid muscle. Ludwig's angina is infection of submandibular space. Etiology - dental infections. They account for 80 percent of the cases. Submandibular sialadenitis, injury to oral mucosa and fractures of the mandible account for other cases. CLINICAL FEATURES- There is marked difficulty in swallowing (odynophagia) with varying degrees of trismus. When infection is localized to the floor of mouth are swollen and tongue seems to be pushed up and back. Usually there is cellulitis of the tissue rather than frank abscess. tongue is progressively pushed upward and backward threatening the airway. laryngeal edema may appear. Rx- Systemic antibiotics. Incision and drainage of abscess. RETROPHARYNGEAL SPACE - It lies behind the pharynx between the buccopharyngeal fascia covering pharyngeal constrictor muscles and the preveebral fascia.it extends from the base of skull to the bifurcation of trachea. The space is divided into two lateral compaments (Space of Gillette) by a fibrous raphe. each lateral space contains retropharyngeal nodes which usually disappear at 3- 4 years of age. Parapharyngeal space communicates with the retropharyngeal space. [/INST] question: Ludwig's angina occurs due to infection of: | options: A: Submandibular space B: Retropharyngeal space C: Pharyngomaxillary space D: Peritonsillar space | answer: A </s>