Protostomes development includes all of the following except :

Options

A. spiral cleavage
B. daughter cells sit in grooves formed by prior cleavage
C. cell fate is fixed and can develop in only one way
D. radial cleavage

Explanation

To solve the question regarding protostome development, let's break down the information step by step:

### Step 1: Understand Protostomes
Protostomes are a group of animals characterized by their embryonic development. In protostomes, the first opening that forms during embryonic development (the blastopore) becomes the mouth.

### Step 2: Identify Key Features of Protostomes
1. **Spiral Cleavage**: In protostomes, the cells divide in a spiral pattern.
2. **Determinate Cleavage**: The fate of each cell is determined early in development; each cell has a specific role.
3. **Solid Ventral Cord**: Protostomes typically have a solid ventral nerve cord.
4. **Daughter Cells Arrangement**: The daughter cells are arranged such that they sit on top of the previous layer of cells.

### Step 3: Compare with Deuterostomes
Deuterostomes, in contrast, have different characteristics:
1. **Radial Cleavage**: Cells divide in a radial pattern.
2. **Indeterminate Cleavage**: The fate of the cells is not predetermined; they can develop into different types of cells.
3. **Hollow Ventral Cord**: Deuterostomes have a hollow ventral nerve cord.

### Step 4: Analyze the Options
The question asks which of the following is **not** included in protostome development. The options provided include:
- Spiral cleavage
- Daughter cells sitting in groups formed by prior cleavage
- Fixed fate of cells (determinate cleavage)
- Radial cleavage

### Step 5: Identify the Incorrect Option
From the characteristics listed:
- Protostomes have spiral cleavage (True).
- Daughter cells do sit in groups formed by prior cleavage (True).
- The fate of cells is fixed (True).
- Protostomes do **not** have radial cleavage; that is a characteristic of deuterostomes (False).

### Conclusion
The correct answer to the question is **radial cleavage**, as this is not a feature of protostome development.

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