Many blue-green algae occur in thermal springs (hot water springs). The temperature tolerance of these algae have been attributed to their

Options

A. Mitochondrial structure
B. Importance of homopolar bonds in their proteins
C. Cell wall structure
D. Modern cell organization

Answer

To answer the question regarding the temperature tolerance of blue-green algae (cyanobacteria) in thermal springs, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Organism**: Recognize that blue-green algae are also known as cyanobacteria, which belong to the kingdom Monera.

2. **Understand Their Habitat**: Note that these organisms are found in extreme environments, such as thermal springs, where temperatures can be quite high.

3. **Consider the Options**: The question provides several options: mitochondrial structure, importance of homopolar bonds, cell wall structure, and modern cell organization.

4. **Research Temperature Tolerance**: Investigate how certain cyanobacteria, such as *Ocellatoria brevis*, are able to survive in high temperatures.

5. **Identify Key Features**: It is found that the ability of these cyanobacteria to tolerate high temperatures is primarily due to the presence of homopolar bonds in their proteins.

6. **Explain the Mechanism**: Homopolar bonds are strong and do not destabilize easily at high temperatures, allowing the proteins to maintain their structure and function even in extreme conditions.

7. **Conclude the Answer**: Therefore, the temperature tolerance of these blue-green algae in thermal springs is attributed to their homopolar bonds.

### Final Answer:
The temperature tolerance of blue-green algae in thermal springs has been attributed to their **importance of homopolar bonds** in their proteins.

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