Mitochondria are absent in

Options

A. Green Algae
B. Brown Algae
C. Blue-Green Algae
D. Red Algae.

Answer

**Step-by-Step Solution:**

1. **Understand the Question:**
The question asks where mitochondria are absent among the given options: green alga, brown alga, blue-green alga, and red alga.

2. **Identify Types of Organisms:**
Organisms are classified into two main categories: prokaryotic and eukaryotic. Prokaryotic organisms lack a true nucleus and membrane-bound organelles, while eukaryotic organisms possess both.

3. **Define Mitochondria:**
Mitochondria are membrane-bound organelles found in eukaryotic cells. They are responsible for energy production and are characterized by having a double membrane.

4. **Analyze Each Option:**
- **Green Alga:** This is a eukaryotic organism and contains mitochondria.
- **Brown Alga:** This is also a eukaryotic organism and contains mitochondria.
- **Blue-Green Alga:** This is actually cyanobacteria, which are prokaryotic organisms. They do not have membrane-bound organelles, including mitochondria.
- **Red Alga:** This is a eukaryotic organism and contains mitochondria.

5. **Conclusion:**
The only organism from the options provided that lacks mitochondria is the blue-green alga (cyanobacteria).

**Final Answer: Blue-green alga (cyanobacteria)**

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