Select the incorrect statement.

Options

A. In the 24 hour average duration of cell cycle of a human cell, division proper lasts for only about an hour.
B. The interphase lasts more than 95% of the duration of cell cycle.
C. Even after S phase the number of chromosomes remains the same , i.e., 2n
D. In plant cell, during the S phase , DNA replication begins in the nucleus, and the centriole duplicates in the cytoplasm.

Answer

To solve the question, we need to analyze each statement provided and identify which one is incorrect.

### Step-by-Step Solution:

1. **Understanding the Cell Cycle**:
- The cell cycle consists of two main phases: Interphase and M phase (mitotic phase).
- Interphase is where the cell spends most of its time (approximately 95% of the cell cycle) preparing for division, which includes growth and DNA replication.

2. **Evaluating Statement 1**:
- **Statement**: "In the 24-hour average duration of cell cycle of a human cell division proper lasts for only about an hour."
- **Analysis**: This statement is correct. The M phase (where cell division occurs) is indeed a small fraction of the entire cell cycle duration.

3. **Evaluating Statement 2**:
- **Statement**: "The interphase lasts more than 95 percent of the duration of the cell cycle."
- **Analysis**: This statement is also correct. Interphase is the longest phase of the cell cycle, comprising the majority of the cycle's duration.

4. **Evaluating Statement 3**:
- **Statement**: "Even after S phase, the number of chromosomes remains the same that is 2n."
- **Analysis**: This statement is correct. During the S phase, DNA is replicated, but the ploidy (number of sets of chromosomes) remains the same. If the cell is diploid (2n) before S phase, it remains diploid after S phase.

5. **Evaluating Statement 4**:
- **Statement**: "In plant cells during the S phase, DNA replication begins in the nucleus and the centriole duplicates in the cytoplasm."
- **Analysis**: This statement is incorrect. In plant cells, there are no centrioles. Centrioles are found in animal cells, where they duplicate during the S phase. In plant cells, DNA replication occurs in the nucleus, but centriole duplication does not happen.

### Conclusion:
The incorrect statement is **Statement 4**.