An organism made up of a single cell is known as a unicellular organism. Which of the following organisms is not unicellular?

Options

A. Bacterium
B. Mushroom
C. Paramecium
D. Dinoflagellate

Answer

To determine which organism is not unicellular, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition**: A unicellular organism is made up of a single cell. In contrast, multicellular organisms are made up of multiple cells.

2. **Identify the Options**: The question provides a list of organisms. We need to analyze each option to see if it is unicellular or multicellular.

3. **Analyze Each Option**:
- **Option 1: Bacterium** - Bacteria are part of the Monera kingdom and are unicellular organisms.
- **Option 2: Mushroom** - Mushrooms are part of the Fungi kingdom and are multicellular organisms.
- **Option 3: Paramecium** - Paramecium belongs to the Protista kingdom and is a unicellular organism.
- **Option 4: Dinoflagellate** - Dinoflagellates are also part of the Protista kingdom and are unicellular organisms.

4. **Determine the Correct Answer**: From the analysis, the only organism that is not unicellular is the mushroom (Option 2).

5. **Conclusion**: The organism that is not unicellular is the mushroom.

### Final Answer:
The organism that is not unicellular is **Option 2: Mushroom**.

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