Schleiden (1838) proposed that cell is the structural and functional unit of life. His idea was a

Options

A. Observation
B. Assumption
C. Generalisation
D. Hypothesis

Answer

To solve the question regarding Schleiden's proposal that the cell is the structural and functional unit of life, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the nature of Schleiden's idea regarding cells in 1838. We need to determine if it was an observation, assumption, generalization, or hypothesis.

2. **Define Key Terms**:
- **Observation**: A statement based on what one sees or notices.
- **Assumption**: A belief or statement taken for granted without proof.
- **Generalization**: A broad statement or conclusion based on specific instances.
- **Hypothesis**: A proposed explanation for a phenomenon, which can be tested through experimentation.

3. **Contextual Background**: Schleiden proposed that all plant tissues are made up of cells, which he observed. This was a significant finding in cell biology. His work was later supported by Schwann, who found similar structures in animal tissues.

4. **Analyzing Schleiden’s Proposal**: Schleiden's assertion was not merely an observation; it was a broader proposition that aimed to explain the structure of living organisms. This aligns with the definition of a hypothesis, as it was a statement that needed to be tested and verified by further research.

5. **Conclusion**: Based on the definitions and the context of Schleiden's work, we can conclude that his idea was best classified as a **hypothesis** (Option D).

### Final Answer:
The correct answer is **D. Hypothesis**.

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