This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Infertility, Subject name: Gynaecology & Obstetrics
Normal sperm concentration in semen analysis should be 
Select and explain. 
A. >= 5 millilon/ml, B. >= 15 millilon/ml, C. >= 20 millilon/ml, D. >= 25 millilon/ml
B: >= 15 millilon/ml
Answer: B: >= 15 millilon/ml 
Explanation: Normal Semen Analysis: World Health Organization Volume>=1.5 mLSperm concentration>=15 million/mL Sperm motility>=32% progressive>25% rapidly progressiveMorphology (strict criteria)>=4% normal formWhite blood cells<1 million/mLReference: Novak's Gynecology; 14th edition; Chapter 32; Infeility and Assisted Reproductive Technology