People recovering from long illness are often advised to include the alga Spirulina in their diet because it:

Options

A. Makes the food easy to digest
B. Is rich in protein and vitamin `B_12`
C. Has antibiotic properties
D. Restores the intestinal flora

Answer

To answer the question regarding why people recovering from long illness are advised to include Spirulina in their diet, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Characteristics of Spirulina**:
- Spirulina is a type of blue-green algae, also known as cyanobacteria. It is microscopic and filamentous in structure.

2. **Nutritional Composition**:
- Spirulina is known for its high nutritional value. It contains a significant amount of protein, with its protein content ranging from 30% to 70% of its dry weight.

3. **Vitamins and Other Nutrients**:
- In addition to being rich in protein, Spirulina is also a good source of vitamin B12, which is essential for various bodily functions, including the formation of red blood cells and maintenance of the nervous system.

4. **Health Benefits**:
- The high protein content and the presence of vitamin B12 make Spirulina particularly beneficial for individuals recovering from illness, as these nutrients can help in tissue repair and recovery.

5. **Conclusion**:
- Based on the nutritional benefits, the correct answer to the question is that Spirulina is included in the diet of people recovering from long illness because it is rich in protein and vitamin B12.

### Final Answer:
People recovering from long illness are often advised to include Spirulina in their diet because it is rich in protein and vitamin B12.

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