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: Unknown
The feature of hemorrhagic disease of the new born is - 
Select and explain. 
A. Prolonged prothrombin time, B. Defective platelet count, C. Decreased bleeding time, D. Prolonged thrombin time
A: Prolonged prothrombin time
Answer: A: Prolonged prothrombin time 
Explanation: Ans. is 'a' Prolonged prothrombin time Hemorrhagic disease of the newborn. It is caused by a deficiency of vitamin K dependent factors (II, VII, IX, X)*. Bleeding occurs in 0.25-1.7% of newborns who do not receive vitamin K prophylaxis after birth. Symptoms - Sites of ecchymoses and surface bleeding include - Gastrointestinal tract Umbilical cord Circumcision site Nose Sometimes intracranial hemorrhage can occur. Laboratory features of hemorrhagic disease of new bom : Platelet count -Normal Prothrombin time -Prolonged* Thrombin time -Normal until very late in the disease* Fibrinogen -Normal Factor V -Normal