Most bacteria are ....... and include major decomposers and pathogens.
(a) chemoheterotrophs
(b) photoheterotrophs
(c) chemoautotrophs
(d) photoautotrophs

Options

A. chemoheterotrophs
B. photoheterotrophs
C. chemoautotrophs
D. photoautotrophs

Explanation

To solve the question, "Most bacteria are ....... and include major decomposers and pathogens," we need to analyze the options provided and understand the characteristics of bacteria.

### Step-by-Step Solution:

1. **Understanding the Question**: The question states that most bacteria are a certain type of organism and highlights that they include major decomposers and pathogens.

2. **Identifying Key Terms**:
- **Decomposers**: These are organisms that break down dead organic matter. They are typically heterotrophic, meaning they cannot produce their own food and rely on other organic substances for nutrition.
- **Pathogens**: These are organisms that cause disease. Many pathogens are also heterotrophic.

3. **Analyzing the Options**:
- **(a) Chemoheterotrophs**: These organisms obtain their energy from chemical compounds and require organic compounds as a carbon source. This fits the description of decomposers and pathogens.
- **(b) Photoheterotrophs**: These organisms use light for energy but still require organic compounds for carbon. While they are heterotrophic, they are not primarily known as major decomposers.
- **(c) Chemoautotrophs**: These organisms obtain energy from chemical reactions and can produce their own food from inorganic sources. They do not fit the description of decomposers or pathogens.
- **(d) Photoautotrophs**: These organisms use light energy to produce their own food from carbon dioxide. They are not heterotrophic and thus do not fit the description.

4. **Conclusion**: Based on the analysis, the correct answer is (a) **chemoheterotrophs**, as they are the type of bacteria that include major decomposers and pathogens.

### Final Answer:
(a) chemoheterotrophs