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: ENT
Definition of sleep apnoea 
Select and explain. 
A. >10 apnoeas during 7 hours of sleep, B. >30 apnoeas during 7 hours of sleep, C. >10 apnoeas during 2 hours of sleep, D. >30 apnoeas during 2 hours of sleep
B: >30 apnoeas during 7 hours of sleep
Answer: B: >30 apnoeas during 7 hours of sleep 
Explanation: None