All the activities of a cell are performed by a single cell in an _________ organism.

Explanation

**Step-by-Step Solution:**

1. **Understand the Question**: The question asks about the type of organism where all activities are performed by a single cell.

2. **Identify Key Terms**: The key term here is "single cell" which indicates that the organism consists of only one cell.

3. **Recall Organism Types**: Organisms can be classified as unicellular (single-celled) or multicellular (many-celled).

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