**Core Concept**
Asthenospermia refers to a condition related to **male infertility**, specifically involving the **quality of sperm**. It is characterized by **reduced sperm motility**.

**Why the Correct Answer is Right**
Since the correct answer is not provided, let's discuss the concept. Asthenospermia is diagnosed when a significant percentage of a man's sperm have **low motility** or are **immotile**. This condition can result from various factors, including **infections**, **hormonal imbalances**, **varicocele**, and **exposure to toxins**.

**Why Each Wrong Option is Incorrect**
**Option A:** Without the specific answer choices, we cannot directly address why each option is incorrect. However, in general, asthenospermia is not about the **number** of sperm but their **motility**.
**Option B:** Similarly, this would be incorrect if it referred to a different aspect of sperm quality, such as **morphology**.
**Option C:** This option would be wrong if it described a condition unrelated to sperm motility.
**Option D:** Without the correct answer, we cannot specify why this option is incorrect, but it would be wrong if it did not accurately describe asthenospermia.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that **asthenospermia** can significantly impact **fertility** because sperm motility is crucial for reaching and fertilizing the egg.

**Correct Answer:** Correct Answer: D. Reduced sperm motility