Which of the following are not a group of green algae ?

Options

A. Chlamydomonas, Volvox
B. Ulothrix, Spirogyra
C. Gelidium, Chara
D. Chlamydomonas and Chara

Answer

To determine which of the following options are not a group of green algae, we will analyze each option based on our knowledge of algae classification.

### Step-by-Step Solution:

1. **Understand the Classification of Algae**:
- Algae are classified into three main groups based on their pigments:
- **Chlorophyceae**: Green algae
- **Rhodophyceae**: Red algae
- **Phaeophyceae**: Brown algae

2. **Evaluate Each Option**:
- **Option 1: Chlamydomonas and Volvox**:
- Both Chlamydomonas and Volvox are classified as green algae (Chlorophyceae).
- **Option 2: Lotrix and Spirogyra**:
- Both Lotrix and Spirogyra are also classified as green algae (Chlorophyceae).
- **Option 3: Gelidium and Chara**:
- Gelidium is classified as red algae (Rhodophyceae), while Chara is a green algae (Chlorophyceae). Since Gelidium is not a green algae, this option contains an organism that is not a green algae.
- **Option 4: Chlamydomonas and Chara**:
- Both Chlamydomonas and Chara are classified as green algae (Chlorophyceae).

3. **Conclusion**:
- The only option that contains an organism that is not classified as green algae is **Option 3: Gelidium and Chara**. Therefore, this is the correct answer to the question.

### Final Answer:
**Option 3: Gelidium and Chara** is not a group of green algae.