`C_(4)` pathway is advantageous over `C_(3)` pathway in plants as it

Options

A. Occurs in relatively low `CO_(2)` concentration
B. Uses more amount of water
C. Occurs in relatively low `O_(2)` concentration
D. Is less efficient in energy utilisation.

Answer

### Step-by-Step Solution:

1. **Understanding C3 and C4 Pathways**:
- The C3 pathway is the most common form of photosynthesis, where carbon dioxide is fixed directly into a 3-carbon compound (3-phosphoglycerate).
- The C4 pathway, on the other hand, involves an additional step where carbon dioxide is first fixed into a 4-carbon compound (oxaloacetate) before being converted into the 3-carbon compound.

2. **Key Advantage of C4 Pathway**:
- The C4 pathway is advantageous because it allows plants to efficiently fix carbon dioxide even when the concentration of carbon dioxide is low. This is particularly beneficial in hot and dry environments.

3. **Photorespiration**:
- In C3 plants, when carbon dioxide levels are low, the enzyme RuBisCO can fix oxygen instead of carbon dioxide, leading to a process called photorespiration, which is wasteful and reduces the efficiency of photosynthesis.
- C4 plants have a mechanism that minimizes photorespiration, allowing them to maintain higher rates of photosynthesis under low carbon dioxide conditions.

4. **Water Use Efficiency**:
- C4 plants can keep their stomata closed for longer periods to conserve water, which is crucial in arid conditions. This adaptation allows them to reduce water loss while still maintaining photosynthesis.

5. **Conclusion**:
- Therefore, the C4 pathway is advantageous over the C3 pathway primarily because it can operate efficiently at relatively low carbon dioxide concentrations, making it more effective in certain environmental conditions.

### Final Answer:
The C4 pathway is advantageous over the C3 pathway in plants as it **occurs in relatively low carbon dioxide concentration**.