Which is correct about cell theory in view of current status of our knowledge about cell structure ?

Options

A. it needs modification due to discovery of subcellular structures like chloroplasts and mitochondria
B. Modified cell theory means that all living beings are composed of cells capable of reproducing
C. Cell theory does not hold good because all living beings do not have cellular organisation (e.g. viruses)
D. Cell theory means that all living objects consist of cells whether or not capable of reproducing

Explanation

### Step-by-step Solution:

1. **Understanding Cell Theory**:
- Cell theory is a fundamental concept in biology that was developed by three scientists: Theodore Schwann, Matthias Schleiden, and Rudolf Virchow.
- The main points of cell theory are:
- All living organisms are composed of cells.
- All cells arise from pre-existing cells (Omnis cellula e cellula).
- Some organisms, like viruses, do not have a cellular organization.

2. **Analyzing the Options**:
- **Option 1**: Suggests that cell theory needs modification due to the discovery of subcellular structures like chloroplasts and mitochondria. This is incorrect because the existence of subcellular structures does not invalidate cell theory.
- **Option 2**: States that modified cell theory means all living beings are composed of cells capable of reproducing. This is misleading as it excludes acellular organisms like viruses.
- **Option 3**: Claims that cell theory does not hold good because all living beings do not have cellular organization (e.g., viruses). This is a correct statement since viruses are not composed of cells and challenge the traditional cell theory.
- **Option 4**: Indicates that cell theory means all living objects consist of cells whether or not capable of reproducing. This is incorrect as it implies that all living entities are cellular, which is not true for viruses.

3. **Conclusion**:
- The correct statement regarding cell theory, in light of current knowledge, is **Option 3**: "Cell theory does not hold good because all living beings do not have cellular organization, e.g., viruses."