To solve the question of which group of algae belongs to the same class, we will categorize the given options based on the types of algae: green algae, brown algae, and red algae.
### Step-by-Step Solution:
1. **Identify the Types of Algae**:
- Algae can be classified into three main types:
- **Green Algae (Chlorophyta)**: Characterized by the presence of chlorophyll A and B, giving them a green color.
- **Brown Algae (Phaeophyta)**: Contains chlorophyll A and C, along with fucoxanthin, which gives them a brown color.
- **Red Algae (Rhodophyta)**: Contains chlorophyll A and phycoerythrin, which gives them a red color.
2. **List the Algae from the Options**:
- **Option 1**: Cara, Fucus, Polysiphonia
- **Option 2**: Wallwax, Spirogyra, Chlamydomonas
- **Option 3**: Porphyra, Ectocarpus, Eurythrix
- **Option 4**: Sargassum, Laminaria, Gracilaria
3. **Classify Each Alga**:
- **Option 1**:
- Cara: Green Algae
- Fucus: Brown Algae
- Polysiphonia: Red Algae
- **Conclusion**: Different classes.
- **Option 2**:
- Wallwax (Wolbox): Green Algae
- Spirogyra: Green Algae
- Chlamydomonas: Green Algae
- **Conclusion**: All are Green Algae (same class).
- **Option 3**:
- Porphyra: Red Algae
- Ectocarpus: Brown Algae
- Eurythrix: Green Algae
- **Conclusion**: Different classes.
- **Option 4**:
- Sargassum: Brown Algae
- Laminaria: Brown Algae
- Gracilaria: Red Algae
- **Conclusion**: Different classes.
4. **Determine the Correct Option**:
- The only option where all members belong to the same class is **Option 2: Wallwax, Spirogyra, and Chlamydomonas**, which are all Green Algae.
### Final Answer:
The correct option is **Option 2: Wallwax, Spirogyra, and Chlamydomonas**.
