**Core Concept**
The question tests the understanding of semen analysis parameters and their correlation with male infertility. **Semen analysis** is a crucial diagnostic tool for evaluating male fertility, assessing parameters such as **sperm count**, **pH**, **volume**, **motility**, and **morphology**.

**Why the Correct Answer is Right**
The correct answer is based on the provided semen analysis results. A **sperm count** of 15 million/ml is lower than the normal range (20 million/ml or more), indicating **oligospermia**. The **pH** is slightly alkaline, which is acceptable. The **volume** is lower than the normal range (1.5 ml or more), and **motility** and **morphology** are within acceptable limits. Given these parameters, **oligospermia** is the most likely diagnosis.

**Why Each Wrong Option is Incorrect**
**Option A:** **Normospermia** is incorrect because the sperm count is below the normal range.
**Option C:** **Azoospermia** refers to the absence of sperm, which is not the case here.
**Option D:** **Aspermia** refers to the absence of semen, which is also not applicable.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that **oligospermia** is defined by a sperm count of less than 20 million/ml and can be a significant factor in male infertility.

**Correct Answer:** B. Oligospermia