Bulk `CO_(2)`fixation occurs in

Options

A. Crop plants
B. oceans
C. tropical rain forests
D. Temperature forests

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks where bulk carbon dioxide (CO₂) fixation occurs. This involves identifying the ecosystem that plays a significant role in absorbing and converting CO₂.

2. **Analyzing the Options**: The options provided are:
- Croplands
- Oceans
- Tropical Rainforest
- Temperate Forest

3. **Evaluating Each Option**:
- **Croplands**: While croplands do contribute to CO₂ fixation through agricultural practices, they are limited in scale compared to natural ecosystems.
- **Oceans**: Oceans are vast and contain a large number of photosynthetic organisms, such as phytoplankton, cyanobacteria, seaweed, and seagrass, which are responsible for a significant portion of global CO₂ fixation.
- **Tropical Rainforest**: Tropical rainforests, like the Amazon, are often referred to as the "lungs of the Earth" due to their high oxygen production. However, they do not fix as much CO₂ as oceans.
- **Temperate Forest**: Similar to tropical rainforests, temperate forests contribute to CO₂ fixation but are not as significant as oceans.

4. **Conclusion**: After evaluating all options, it is clear that the oceans, due to their vast area and the presence of numerous photosynthetic organisms, are the primary site for bulk CO₂ fixation.

5. **Final Answer**: Therefore, the correct answer is **Oceans**.

---