The largest alga is

Options

A. Microcystis
B. Macrocystis
C. Red alga
D. Blue-green alga

Answer

To determine the largest alga, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Options**: The question provides four options: microcystis, macrocystis, red alga, and blue-green alga.

2. **Understand the Classification**: The largest algae belong to a specific group within the plant kingdom. Algae can be classified into different phyla based on their characteristics.

3. **Focus on Pheophyceae**: The largest algae are typically found in the phylum Pheophyceae, which is known for its brown algae.

4. **Identify the Genus**: Within the Pheophyceae, the genus that represents the largest brown alga is Macrocystis.

5. **Conclusion**: Based on the classification and the information about the largest algae, the correct answer is Macrocystis.

### Final Answer:
The largest alga is **Macrocystis**.

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