**Core Concept:** The World Health Organization (WHO) has established criteria for assessing semen parameters, including sperm count. The WHO classification system is widely used in clinical practice and research.

**Why the Correct Answer is Right:** According to the 5th edition of the WHO Laboratory Manual for the Examination and Processing of Human Semen, the minimum normal sperm count (also known as total sperm count) is defined as:

**Correct Answer: D**

**Correct Answer: <10 million/mL** This value is derived from the WHO criteria, which are based on the semen analysis of a large number of men from various populations. The normal range for total sperm count is determined as follows: **Why each wrong option is incorrect:** A. **5 million/mL**: This value is too low and falls below the minimum normal sperm count as defined by the WHO. B. **40 million/mL**: This value is too high and does not represent the upper limit of the normal range. C. **20 million/mL**: This value is also too high, falling within the upper limit of the normal range but not representing the minimum value. **Why the correct answer is right:** The minimum normal sperm count of 10 million/mL ensures that semen samples with a count below this value are considered subnormal, indicating potential fertility issues. This value is based on the WHO criteria, which are considered the gold standard in determining normal semen parameters. **Why each wrong option is not right:** A. A sperm count of 5 million/mL is too low, and semen samples with counts below this value are classified as oligospermic (low sperm count). B. A sperm count of 40 million/mL is too high, and semen samples with counts above this value are considered hyperospermic (excessive sperm count). C. A sperm count of 20 million/mL is also too high, falling within the upper limit of the normal range but not representing the minimum value according to the WHO criteria. **Clinical Pearl:** The WHO criteria for normal sperm count provide a comprehensive range of semen parameters, including sperm concentration, motility, and morphology, to ensure accurate diagnosis and treatment planning for male infertility patients. A thorough evaluation of semen parameters is essential for assessing male fertility potential and guiding appropriate management strategies.