Bacteria were regarded to be plants because

Options

A. Some of them are green
B. They are present every where
C. Some of them cannot move
D. They have a rigid cell wall.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks why bacteria were historically classified as plants. We need to identify the characteristics that led to this classification.

2. **Identifying Common Features**: One of the main features that bacteria share with plants is the presence of a cell wall. Both bacteria and plants have a rigid structure surrounding their cells.

3. **Composition of Cell Walls**: The cell wall in bacteria is primarily made up of peptidoglycan, while in plants, it is made of cellulose. This structural similarity is significant in the classification of organisms.

4. **Function of the Cell Wall**: The cell wall provides shape and support to both bacterial and plant cells. This functional similarity further supports the idea that bacteria could be classified alongside plants.

5. **Exclusion of Other Options**: The other options provided in the question (some bacteria being green, their ubiquity, and their inability to move) do not provide a strong basis for classifying bacteria as plants. The defining characteristic is the rigid cell wall.

6. **Conclusion**: Therefore, the reason bacteria were regarded as plants is due to their rigid cell wall, which is a common feature shared with plants.

**Final Answer**: Bacteria were regarded to be plants because they have a rigid cell wall.

---