In human sperm , nebenkern refers to

Options

A. Post acrosomal sheath
B. Mitochondrial spiral
C. Proximal centriole
D. Axial filament

Answer

### Step-by-Step Solution:

1. **Understanding the Context**: The question asks about the term "nebenkern" in relation to human sperm. Recognizing that "nebenkern" is a biological term related to sperm structure is essential.

2. **Identifying the Structure**: In human sperm, the nebenkern refers to a specific formation associated with mitochondria. It is important to know that sperm cells are specialized cells that have unique structures.

3. **Formation of the Nebenkern**: After the process of meiosis, the mitochondria from the spermatid (the precursor cell to sperm) gather on one side of the haploid pronucleus. This is a crucial step in the development of the sperm.

4. **Aggregation of Mitochondria**: The gathered mitochondria fuse together to form large aggregates. This aggregation is a significant part of the formation of the nebenkern.

5. **Final Structure**: These aggregated mitochondria wrap around each other to form a spherical structure known as the nebenkern. This structure is essential for the energy supply needed for sperm motility.

6. **Conclusion**: The nebenkern in human sperm refers specifically to the mitochondrial spiral formed by the aggregation of mitochondria.

### Answer:
The nebenkern in human sperm refers to the **mitochondrial spiral**.