Receptors for sperm binding in mammals are present on :

The correct answer is Zona pellucida.

Step-by-step Explanation:
1. Understanding fertilization in mammals: During the process of fertilization in mammals, the sperm must bind to and penetrate the outer protective layers of the egg (oocyte) to fuse with it.
2. What is the Zona Pellucida? The zona pellucida is a specialized extracellular matrix surrounding the mammalian oocyte. It is composed of glycoproteins (such as ZP1, ZP2, ZP3, and ZP4).
3. Role of receptors: The zona pellucida contains specific glycoprotein receptors (specifically ZP3 in many mammals) that bind to the proteins present on the head of the sperm. This binding is species-specific and triggers the acrosome reaction, allowing the sperm to penetrate the egg.
4. Analyzing other options:
- Corona radiata is the outermost layer of follicular cells surrounding the oocyte, which the sperm must pass through first, but the primary receptors for sperm binding are located on the zona pellucida.
- Vitelline membrane is the membrane of the egg in non-mammalian animals (equivalent to the plasma membrane in mammals).
- Perivitelline space is the fluid-filled space between the zona pellucida and the cell membrane of the oocyte, not a binding site.
Therefore, the receptors for sperm binding in mammals are located on the Zona pellucida.