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
Which of the following depicts the usual order of extraction of teeth if serial  extraction is chosen as the treatment to alleviate severe crowding? 
Select and explain. 
A. Primary second molars, primary first molars, permanent first premolars, primary canines, B. Primary canines, primary first molars, permanent first premolars, C. Primary first molars, primary second molars, primary canines, D. Primary canines, permanent canines, primary first molars, permanent first premolars
B: Primary canines, primary first molars, permanent first premolars
Answer: B: Primary canines, primary first molars, permanent first premolars 
Explanation: Primary canines are extracted to encourage alignment of the crowded incisors. However, the incisors align and upright, borrowing space otherwise needed for eruption of the permanent canine. Primary first molars are then extracted to encourage eruption of the first premolar so it may be extracted to make room for the permanent canine to erupt. These are followed by the permanent first premolar. 
Textbook of ORTHODONTICS Sridhar Premkumar