The factors affecting photosynthesis are
number and size of leaves.
age and orientation of leaves.
amount of chlorophyll.
amount of `CO_2` and `O_2`.
Select the correct option.

Options

A. I,II and IV
B. II,IV and I
C. I,II and III
D. All of these

Answer

### Step-by-Step Solution:

1. **Understanding Photosynthesis**:
- Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy in the form of glucose, using carbon dioxide and water.

2. **Identifying Factors Affecting Photosynthesis**:
- Several factors influence the rate of photosynthesis, including:
- **Number and Size of Leaves**: More leaves and larger leaves increase the surface area for light absorption.
- **Age and Orientation of Leaves**: Younger leaves are generally more efficient in photosynthesis, and the orientation can affect light capture.
- **Amount of Chlorophyll**: Chlorophyll is essential for capturing light energy; more chlorophyll means more light absorption.
- **Amount of CO₂ and O₂**: The concentration of carbon dioxide affects the rate of photosynthesis, while oxygen is a byproduct.

3. **Analyzing Each Factor**:
- **Number and Size of Leaves**: More and larger leaves provide a greater surface area for light absorption, enhancing photosynthesis.
- **Age and Orientation of Leaves**: Younger leaves are more efficient, and their orientation can maximize light exposure.
- **Amount of Chlorophyll**: A higher concentration of chlorophyll allows for more effective light absorption, which is crucial for photosynthesis.
- **Amount of CO₂ and O₂**: The availability of carbon dioxide directly influences the rate of photosynthesis, while oxygen levels can affect the process indirectly.

4. **Conclusion**:
- All the mentioned factors (number and size of leaves, age and orientation of leaves, amount of chlorophyll, and amount of CO₂ and O₂) are indeed important in affecting the rate of photosynthesis.

5. **Selecting the Correct Option**:
- Since all the factors listed are correct, the answer is **Option D**: All of the above.