Assertion:Holoblastic cleavage with almost equal sized blastomeres is a characteristic of placental animals.
Reason: Eggs of most mammals, including humans, are of centrolecithal type.

Options

A. If both assertion and reason are true and the reason is the correct explanation of the assertion, then mark a.
B. if both assertion and reason are ture but the reason is not the correct explanation of assertion, then mark b.
C. if assertion is true statement but reason is false, then mark c.
D. If both assertion and reason are false statements, then mark d.

Answer

### Step-by-Step Solution

1. **Understanding the Assertion**: The assertion states that "Holoblastic cleavage with almost equal sized blastomeres is a characteristic of placental animals."
- Holoblastic cleavage refers to the type of cleavage where the entire egg is divided into smaller cells (blastomeres) completely. This type of cleavage is indeed characteristic of placental mammals, including humans, where the cleavage results in blastomeres that are relatively equal in size.

2. **Understanding the Reason**: The reason provided is "Eggs of most mammals, including humans, are of centrolecithal type."
- Centrolecithal eggs have a large central yolk and are typically found in some invertebrates, not in most mammals. In mammals, including humans, the eggs are classified as microlecithal, meaning they have a small amount of yolk distributed evenly throughout the cytoplasm.

3. **Evaluating the Truth of the Statements**:
- The assertion is true because holoblastic cleavage with equal-sized blastomeres is indeed a characteristic of placental animals.
- The reason is false because the eggs of most mammals, including humans, are not centrolecithal; they are microlecithal.

4. **Conclusion**: Based on the evaluation:
- The assertion is true, but the reason is false. Therefore, the correct answer is option C: "Assertion is true but reason is false."