In human, cleavage divisions are:

Options

A. (a) slow and synchronous
B. (b) Fast and synchronous
C. (c) Slow and asynchronous
D. (d) Fast and asynchronous

Explanation

**Step-by-Step Solution:**

1. **Understanding Cleavage Divisions**: Cleavage divisions refer to the series of rapid mitotic divisions that occur immediately after fertilization. In humans, these divisions lead to the formation of a multicellular embryo.

2. **Stages of Cleavage**: After fertilization, the zygote undergoes several stages: 2-cell stage, 4-cell stage, 8-cell stage, morula, blastula, early gastrula, and gastrula. Each of these stages represents a point in the cleavage process.

3. **Nature of Cell Division**: The cleavage divisions in humans are characterized by rapid mitotic divisions. However, this rapid division is only true up to the blastula stage. After the blastula stage, the rate of division slows down.

4. **Pattern of Division**: The cleavage divisions in humans are not synchronous, meaning they do not occur at the same time for all cells. Instead, they are asynchronous and often unequal. This means that the cells do not divide into equal halves, leading to variations in cell size.

5. **Type of Cleavage**: The type of cleavage that occurs in humans is referred to as holoblastic cleavage. This means that the entire egg is involved in the cleavage process, resulting in multiple smaller cells.

6. **Evaluating Options**:
- Option A (slow and synchronous) is incorrect because while the divisions are slow, they are not synchronous.
- Option B (fast and synchronous) is incorrect as the divisions are not fast.
- Option C (slow and asynchronous) is correct because the divisions are indeed slow and do not occur in a synchronous manner.
- Option D (fast and asynchronous) is incorrect because the divisions are not fast.

7. **Conclusion**: The correct answer to the question is Option C: "slow and asynchronous."

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