In which of the following, placenta development can not be seen?

Options

A. Human
B. Columba
C. Horse
D. Cattle

Answer

To solve the question "In which of the following, placenta development can not be seen?", we need to analyze the options provided and determine which organism does not exhibit placental development.

### Step-by-Step Solution:

1. **Understanding Placenta Development**:
- Placenta development is a characteristic primarily found in mammals. It allows for the exchange of nutrients and waste between the mother and the developing fetus.

2. **Identifying the Organisms**:
- The question presents multiple options, and we need to identify which of these belong to mammals and which do not.

3. **Analyzing the Options**:
- **Humans**: Humans are mammals and exhibit placental development.
- **Columba**: Columba refers to pigeons, which belong to the class Aves (birds). Birds do not develop a placenta.
- **Horse**: Horses are mammals and exhibit placental development.
- **Cattle**: Cattle are also mammals and exhibit placental development.

4. **Conclusion**:
- Among the options, Columba is the only organism that does not exhibit placental development as it belongs to the Aves class. Therefore, the correct answer is **Columba**.

### Final Answer:
The organism in which placenta development cannot be seen is **Columba**.