This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
Ugly duckling stage affects 
Select and explain. 
A. Maxillary anterior teeth, B. Mandibular anterior teeth, C. Both maxillary and mandibular teeth, D. Vertical height of face
A: Maxillary anterior teeth
Answer: A: Maxillary anterior teeth 
Explanation: The Broadbent's Phenomenon - Ugly Duckling Stage (8-11 years)
Around the age of 8 years, a midline diastema is commonly seen in the upper arch, which is usually misinterpreted by the parents as a malocclusion. Crowns of canines in young jaws impinge on developing lateral incisor roots, thus driving the roots medially and causing the crowns to flare laterally. The roots of the central incisors are also forced together, thus causing a maxillary midline diastema. The period from the eruption of lateral incisor to canine is termed as the Ugly Duckling stage. It is an unaesthetic metamorphosis, which eventually leads to an aesthetic result. With eruption of canines, the impingement from the roots shifts incisally, thus driving the incisor crowns medially, resulting in closure of the diastema.
Textbook of Orthodontics, Gurkeerat Singh, 2nd Ed, pg-46