The vast majority of bacteria are:-

Options

A. Symbiotic
B. Autotrophytic
C. Heterotrophic
D. Nitrogen fixing

Answer

**Step-by-Step Solution:**

1. **Understanding Bacteria**: Begin by recognizing that bacteria are unicellular microorganisms that can have various modes of nutrition.

2. **Modes of Nutrition**: Bacteria can be classified based on how they obtain their food. The two main categories are:
- **Autotrophs**: These bacteria can produce their own food through processes like photosynthesis.
- **Heterotrophs**: These bacteria cannot produce their own food and must obtain it from other sources.

3. **Identifying the Majority**: When considering the vast majority of bacteria, it is essential to note that most bacteria fall under the heterotrophic category.

4. **Types of Heterotrophic Bacteria**: Heterotrophic bacteria can be further classified into:
- **Parasitic Bacteria**: These bacteria derive nutrients from living hosts.
- **Saprophytic Bacteria**: These bacteria decompose dead organic matter, playing a crucial role in nutrient cycling.
- **Symbiotic Bacteria**: These bacteria engage in mutual relationships with other organisms (e.g., Rhizobium with legumes).

5. **Conclusion**: Since the majority of bacteria are heterotrophs, the correct answer to the question is that the vast majority of bacteria are heterotrophs.

**Final Answer**: The vast majority of bacteria are heterotrophs.

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