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
Brittle bone syndrome is caused by 
Select and explain. 
A. Improper synthesis of procollagen, B. Polymerisation of collagen, C. Increased osteoclastic activity, D. Increased fibroblastic activity
A: Improper synthesis of procollagen
Answer: A: Improper synthesis of procollagen 
Explanation: None