Assertion : In the beginning, the developmental stages or embryos of animals are alike.
Reason : Ontogeny recapitulates phylogeny.

Options

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

Explanation

**Step-by-Step Solution:**

1. **Understanding the Assertion:**
- The assertion states that the developmental stages or embryos of animals are alike in the beginning. This means that during the early stages of development, embryos of different species exhibit similar characteristics or structures.

2. **Exploring the Reason:**
- The reason provided is "Ontogeny recapitulates phylogeny." This phrase suggests that the development of an individual organism (ontogeny) reflects the evolutionary history (phylogeny) of that organism's species. Essentially, the stages of embryonic development mirror the stages of evolutionary development.

3. **Examining Examples:**
- Various animals, such as fish, horses, calves, and humans, show similar embryonic structures in their early development. For instance, all these embryos may have structures like a post-anal tail and pharyngeal pouches, which resemble gill structures.

4. **Connecting Assertion and Reason:**
- The similarity in the early developmental stages of embryos (assertion) can be explained by the concept of ontogeny recapitulating phylogeny (reason). This means that the shared characteristics in embryos are indicative of common ancestry among different species.

5. **Conclusion:**
- Both the assertion and the reason are correct. The assertion about the similarity of embryos in early development is supported by the reason that ontogeny reflects phylogeny. Therefore, the correct answer is that both the assertion and reason are true, and the reason is the correct explanation for the assertion.

**Final Answer:**
Both assertion and reason are true, and the reason is the correct explanation of the assertion.

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