The boundaries of which of the following kingdom is not well defined ?

Options

A. Plantae
B. Fungi
C. Monera
D. Protista

Answer

To solve the question regarding which kingdom has boundaries that are not well defined, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question asks which kingdom's boundaries are not well defined. This implies that the organisms within this kingdom may share characteristics with organisms from other kingdoms.

2. **Identify the Options**: The options provided are:
- Plantae
- Fungi
- Monera
- Protista

3. **Recall the Five Kingdom Classification**: The five kingdom classification system, proposed by R.H. Whittaker, includes:
- **Plantae**: Multicellular, autotrophic organisms (plants).
- **Fungi**: Mostly multicellular, heterotrophic organisms (fungi).
- **Monera**: Unicellular organisms, including bacteria.
- **Protista**: A diverse group of mostly unicellular organisms that can be autotrophic or heterotrophic.
- **Animalia**: Multicellular, heterotrophic organisms (animals).

4. **Analyze the Characteristics of Each Kingdom**:
- **Plantae**: Well-defined characteristics (e.g., photosynthesis).
- **Fungi**: Well-defined characteristics (e.g., absorption of nutrients).
- **Monera**: Well-defined characteristics (e.g., prokaryotic cells).
- **Protista**: This kingdom is known for its diversity. It includes organisms that can be autotrophic (like Euglena) or heterotrophic (like Amoeba), making it difficult to categorize them strictly as plants or animals.

5. **Conclusion**: Since Protista includes a wide variety of organisms with overlapping characteristics from other kingdoms, it does not have well-defined boundaries. Therefore, the answer to the question is **Protista**.

### Final Answer:
The boundaries of the kingdom that is not well defined is **Protista**.