All eukaryotic unicellular organisms belong to :
(a) Monera
(b) Protista
(c) Fungi
(d) Bacteria

Options

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

Explanation

To solve the question "All eukaryotic unicellular organisms belong to:", we need to analyze the options provided and identify which kingdom includes only eukaryotic unicellular organisms.

### Step-by-Step Solution:

1. **Understand the Question**: The question is asking for the classification of all eukaryotic unicellular organisms. Eukaryotic organisms are characterized by having a true nucleus.

2. **Evaluate Option (a) Monera**:
- Monera includes prokaryotic organisms, which do not have a true nucleus.
- Although Monera includes unicellular organisms, they are not eukaryotic.
- **Conclusion**: Monera is not the correct option.

3. **Evaluate Option (b) Protista**:
- Protista includes unicellular eukaryotic organisms.
- Organisms in this kingdom possess a true nucleus and can be both unicellular and multicellular.
- **Conclusion**: Protista is a strong candidate for the correct answer.

4. **Evaluate Option (c) Fungi**:
- Fungi are primarily multicellular organisms, although some, like yeast, are unicellular.
- However, fungi are not exclusively unicellular and include many multicellular forms.
- **Conclusion**: Fungi is not the correct option as it does not exclusively represent unicellular eukaryotes.

5. **Evaluate Option (d) Bacteria**:
- Bacteria are prokaryotic organisms and do not have a true nucleus.
- While they are unicellular, they do not fit the criteria of being eukaryotic.
- **Conclusion**: Bacteria is not the correct option.

6. **Final Conclusion**:
- The only option that correctly identifies the kingdom containing all eukaryotic unicellular organisms is **(b) Protista**.

### Final Answer:
(b) Protista