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: Pathology
The use of broad-spectrum antibiotics can produce a bleeding diathesis characterized by hematomas, hematuria, melena, and bleeding from the gums by decreasing the normal gut flora and inducing a deficiency of: 
Select and explain. 
A. Vitamin A, B. Vitamin B1, C. Vitamin B6, D. Vitamin K
D: Vitamin K
Answer: D: Vitamin K 
Explanation: A deficiency of vitamin K, which can result from fat malabsorption, broad-spectrum antibiotics, or diffuse liver disease, produces a bleeding diathesis characterized by hematomas, ecchymoses, hematuria, melena, and bleeding from the gums. Laboratory tests reveal an increased bleeding with prolonged PT and PTT and normal bleeding time.