Assertion: The third cleavage in frog is latitudinal
Reason: The mitotic spindle orients parallel to the polar axis.

Options

A. If both Assertion and Reason are true and Reason is correct explanation of Assertion.
B. If both Assertion and Reason are true but Reason is not correct explanation of Assertion
C. If Assertion is true but Reason is false
D. If both Assertion and Reason are false

Answer

To solve the question regarding the assertion and reason about frog cleavage, we can break it down step by step.

### Step-by-Step Solution:

1. **Understand the Assertion**:
- The assertion states that "The third cleavage in frog is latitudinal."
- In frog embryonic development, the first two cleavages are vertical and equal, while the third cleavage is indeed latitudinal and unequal.

2. **Understand the Reason**:
- The reason states that "The mitotic spindle orients parallel to the polar axis."
- The mitotic spindle is responsible for chromosome segregation during cell division. Its orientation affects the direction of the cleavage furrow.

3. **Analyze the Relationship**:
- The assertion is true because the third cleavage in frogs is latitudinal.
- The reason is also true because the orientation of the mitotic spindle does influence the cleavage pattern. When the spindle is oriented parallel to the polar axis, it leads to a latitudinal cleavage.

4. **Determine the Correct Option**:
- Since both the assertion and reason are true, and the reason correctly explains the assertion, the correct option is: "Both assertion and reason are true, and reason is a correct explanation of assertion."

### Final Answer:
- The correct option is: Both assertion and reason are true, and reason is a correct explanation of assertion.