State: Four symptoms of Down's syndrome.

Answer

**Step-by-Step Text Solution:**

1. **Understanding Down's Syndrome**: Down's syndrome is a genetic disorder caused by the presence of an extra chromosome 21, a condition known as trisomy 21. This genetic anomaly leads to various physical and cognitive symptoms.

2. **Identifying Symptoms**: The question asks for four symptoms of Down's syndrome. We will list them based on common knowledge and medical literature.

3. **Listing the Symptoms**:
- **Mental Retardation**: Individuals with Down's syndrome often experience varying degrees of intellectual disability, which can affect their learning and development.
- **Growth Abnormalities**: Many children with Down's syndrome exhibit growth delays, which can lead to shorter stature compared to their peers.
- **Constantly Open Mouth**: A physical characteristic often observed in individuals with Down's syndrome is a tendency to keep their mouths open, which can be due to hypotonia (decreased muscle tone).
- **Dwarfness**: This refers to shorter height than average for their age group, which is a common trait in individuals with Down's syndrome.

4. **Conclusion**: These symptoms can vary in severity among individuals, but they are commonly associated with Down's syndrome.