**Core Concept**
The World Health Organization (WHO) provides guidelines for semen analysis to assess male fertility. These criteria include parameters such as sperm count, sperm morphology, and motility.

**Why the Correct Answer is Right**
The WHO criteria for semen analysis do not include a specific volume requirement. In fact, the WHO manual for semen analysis (5th edition) states that the semen volume should be at least 1.5 mL, but this is not an essential criterion. The correct answer is **B. Volume > 1 ml**, as this value is considered insufficient according to the WHO guidelines.

**Why Each Wrong Option is Incorrect**
**Option A:** A sperm count of > 20 million / ml is indeed an essential criterion according to the WHO, as it is a key indicator of male fertility.

**Option C:** Sperm with normal morphology (strict criteria) > 15% is also an essential criterion, as it reflects the proportion of sperm with normal shape and structure.

**Option D:** Motility > 25% with rapidly progressive motility is an essential criterion, as it indicates the proportion of sperm that are moving and capable of fertilizing an egg.

**Clinical Pearl / High-Yield Fact**
The WHO manual for semen analysis (5th edition) provides specific criteria for each parameter, which are essential for evaluating male fertility. It is crucial to understand these criteria to accurately interpret semen analysis results.

**✓ Correct Answer: B. Volume > 1 ml**