Cell theory is applicable to all except

Options

A. Animals
B. Plants
C. Fungi
D. Viruses

Answer

### Step-by-Step Solution:

1. **Understanding Cell Theory**:
- Cell theory states that all living organisms are composed of cells, which are the basic units of life. This theory applies to all forms of life, including animals, plants, and fungi.

2. **Evaluating the Options**:
- The options provided are animals, plants, fungi, and viruses. We need to determine which of these does not fit within the framework of cell theory.

3. **Analyzing Viruses**:
- Viruses are unique entities that do not possess the characteristics of living cells. They cannot reproduce independently and require a host cell to replicate. This dependency on a host for reproduction is a significant factor that differentiates them from other living organisms.

4. **Conclusion**:
- Since viruses do not meet the criteria of being composed of cells and cannot reproduce on their own, they are not considered living organisms in the same way that animals, plants, and fungi are. Therefore, cell theory does not apply to viruses.

5. **Final Answer**:
- The correct answer is that cell theory is applicable to all except **viruses**.