Cell theory was formulated by

Options

A. Schleiden and Schwann
B. Virchow
C. Hooke
D. Haeckel

Explanation

**Step-by-Step Solution:**

1. **Understanding Cell Theory**: The cell theory is a fundamental concept in biology that describes the properties and functions of cells. It is essential to know the main postulates of this theory.

2. **Identifying the Original Postulates**: The original cell theory had two main postulates:
- All living organisms are made up of one or more cells.
- The cell is the basic unit of life.

3. **Contributors to Cell Theory**: The cell theory was primarily formulated by two scientists:
- Mathias Schleiden (not Skelton) contributed to the idea that all plants are composed of cells.
- Theodor Schwann (not Schon) extended this idea to animals, stating that all animals are also made of cells.

4. **Addition of a Third Postulate**: Later, Rudolf Virchow added a third postulate to the cell theory, which states that all cells arise from pre-existing cells.

5. **Conclusion**: Therefore, the cell theory was formulated by Mathias Schleiden and Theodor Schwann, with Rudolf Virchow contributing an additional postulate later.

**Final Answer**: The cell theory was formulated by Mathias Schleiden and Theodor Schwann.

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