Assertion : Cyclis pathway of photosythesis first apperead in some eubacterial species.
Reason Oxygen started accumulating in the atmosphere after the nonj-cyclic pathway of photosynthesis evolved.

Options

A. If both assertion and reason are true and reason is the correct explaination of assertion
B. If both assertion and reason are true but reason is not correct explaination of assertion
C. If assertion is true but reason is false
D. If both assertion and reason are false.

Explanation

To solve the assertion and reason question, we need to analyze both statements carefully.

### Step 1: Analyze the Assertion
The assertion states that "the cyclic pathway of photosynthesis first appeared in some eubacterial species."

- The cyclic pathway of photosynthesis is indeed believed to have evolved in some early photosynthetic bacteria, particularly in eubacteria. This pathway involves the use of light energy to produce ATP but does not produce oxygen.

**Conclusion**: The assertion is true.

### Step 2: Analyze the Reason
The reason states that "oxygen started accumulating in the atmosphere after the non-cyclic pathway of photosynthesis evolved."

- The non-cyclic pathway of photosynthesis (also known as the Z-scheme) involves the photolysis of water, which produces oxygen as a byproduct. This process is responsible for the accumulation of oxygen in Earth's atmosphere, particularly during the Great Oxygenation Event.

**Conclusion**: The reason is also true.

### Step 3: Determine the Relationship
Now we need to determine if the reason explains the assertion.

- While both statements are true, the reason does not explain why the cyclic pathway appeared in eubacterial species. The cyclic pathway is more about ATP production without oxygen release, while the reason focuses on the oxygen-producing non-cyclic pathway.

### Final Conclusion
Both the assertion and reason are true, but the reason does not provide a correct explanation for the assertion. Therefore, the correct answer is:

**Option B**: Both assertion and reason are true, but reason is not the correct explanation of the assertion.

---