All living organisms are made up of cells. Cells are often referred to as the building blocks of life. Which of the following organisms is not a unicellular organism?

Options

A. Bacteria
B. Coral
C. Yeast
D. Archaea

Answer

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

### Step-by-Step Solution:

1. **Understand the Definition of Unicellular and Multicellular Organisms**:
- Unicellular organisms consist of a single cell that performs all necessary functions for life.
- Multicellular organisms are made up of multiple cells that work together to perform various functions.

2. **Identify the Organisms Listed in the Question**:
- The question provides a list of organisms, which typically includes options like bacteria, corals, fungi, and archaea.

3. **Classify Each Organism**:
- **Bacteria**: These are unicellular organisms. They consist of a single cell and are classified as prokaryotes.
- **Corals**: These are multicellular organisms. They are part of the phylum Cnidaria and are typically found in aquatic environments.
- **Fungi (e.g., yeast)**: Some fungi are unicellular (like yeast), while others are multicellular (like mushrooms).
- **Archaea**: Similar to bacteria, archaea are also unicellular organisms that often thrive in extreme environments.

4. **Determine Which Organism is Not Unicellular**:
- From the classifications, we see that corals are the only multicellular organisms among the options provided.

5. **Conclude the Answer**:
- Therefore, the organism that is not a unicellular organism is **corals**.

### Final Answer:
The organism that is not a unicellular organism is **corals**.

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