One way cycle is

Options

A. carbon cycle
B. water cycle
C. free energy cycle
D. `O_(2)` cycle

Answer

### Step-by-Step Solution:

1. **Understanding Cycles in Ecosystems**:
- In ecosystems, cycles refer to the movement of elements and energy through various forms and organisms. Common cycles include the carbon cycle, water cycle, and oxygen cycle.

2. **Identifying Cyclic Processes**:
- The carbon cycle involves carbon dioxide being absorbed by plants, which are then consumed by animals. Both plants and animals release carbon dioxide back into the atmosphere, completing the cycle.
- The water cycle involves water vapor condensing to form rain, which fills water bodies and is used by plants and animals. These organisms return water vapor to the atmosphere through processes like transpiration and evaporation.

3. **Defining One-Way Cycles**:
- A one-way cycle refers to the flow of energy that does not return to its original state. An example of this is the free energy cycle, where energy flows from sunlight to plants, then to herbivores (like deer), and finally to carnivores (like tigers). Once energy is transferred, it does not return to the plants.

4. **Analyzing the Free Energy Cycle**:
- In the free energy cycle, energy is captured by plants from sunlight and is then transferred through the food chain. This energy is utilized by each organism but is ultimately lost as heat and cannot return to the original source.

5. **Conclusion**:
- Among the cycles discussed, the free energy cycle is the only one that is a one-way process, as energy does not cycle back to its starting point.

### Final Answer:
The one-way cycle is the **free energy cycle**.

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