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: Surgery
Following genetic counseling in a family for Familial polyposis coli for a 15 year old person, APC gene mutation is present. Next step of screening is 
Select and explain. 
A. colonoscopy from now, B. Colonoscopy from 10 years before the detection of Ca. In family, C. Occult blood in stools every year till 30 years., D. CECT + colonoscopy
A: colonoscopy from now
Answer: A: colonoscopy from now 
Explanation: If APC gene mutation is present colonoscopy done from 10 years of age.