Read the following text and answer the following questions on the basis of the same:
During sexual reproduction, the male inserts the sperm into the female reproductive tract, and sperm receive by the ovary and after that sperm fuse with the egg (ovum) in the ampullary region, this process is called fertilization, haploid nucleus of sperm fuse with that of ovum to form Diploid zygote.
The phenomenon of sperm activation in mammals is known as.

Options

A. Parthenogenesis
B. Amphimixis
C. Capacitation
D. Acrosomal reaction

Explanation

To answer the question about the phenomenon of sperm activation in mammals, we can break down the information provided in the text and the video transcript step by step.

### Step-by-Step Solution:

1. **Understanding Fertilization**: The process of fertilization occurs when the male sperm fuses with the female ovum (egg) in the ampullary region of the female reproductive tract. This fusion results in the formation of a diploid zygote.

2. **Identifying Sperm Activation**: The question specifically asks about the phenomenon of sperm activation in mammals. Sperm activation is crucial for the sperm to become capable of fertilizing the egg.

3. **Options Given**: The options provided in the video transcript are:
- Parthenogenesis
- Capacitation
- Acrosomal reaction

4. **Analyzing Each Option**:
- **Parthenogenesis**: This is a form of asexual reproduction where an egg develops into an organism without fertilization. This does not relate to sperm activation.
- **Capacitation**: This is the process that occurs in the female reproductive tract where sperm undergo physiological changes that enable them to fertilize an egg. It involves changes in the sperm plasma membrane due to factors like calcium ions, making the sperm fertile.
- **Acrosomal Reaction**: This is the reaction that occurs when the sperm reaches the egg, where enzymes from the acrosome help the sperm penetrate the egg's outer layers. While important for fertilization, it is not the initial activation of sperm.

5. **Conclusion**: Based on the analysis, the correct answer to the question about the phenomenon of sperm activation in mammals is **Capacitation**.

### Final Answer:
The phenomenon of sperm activation in mammals is known as **Capacitation**.