Which of the following statements is incorrect ?

Options

A. Mitochondria, unless specifically stained are not easily visible under the microscope.
B. Physiological activity of cells determines the number of mitochondria per cell.
C. Mitochondrion, a power house of cell has DNA, RNA, ribosomes and enzymes, so it can survive outside the cell.
D. Mitochondria divide by fission.

Answer

To determine which statement about mitochondria is incorrect, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement 1**: "Mitochondria, unless it is specifically stained, are not visible under the microscope."
- This statement is **correct**. Mitochondria are typically not visible without specific staining techniques, such as using Janus green, which allows them to be seen under a microscope.

2. **Statement 2**: "The physiological activity of the cell determines the number of mitochondria per cell."
- This statement is also **correct**. The number of mitochondria in a cell correlates with its activity level. Active cells, which require more energy, will have a higher number of mitochondria to meet their ATP demands.

3. **Statement 3**: "Mitochondria is the powerhouse of the cell because it synthesizes ATP, contains DNA in its matrix, contains RNA, contains ribosomes which are of the 70S type, contains enzymes, but it cannot survive outside the living cell."
- This statement is **incorrect**. While it is true that mitochondria have their own DNA, RNA, ribosomes, and enzymes, they are considered semi-autonomous organelles. They can perform some functions independently but are still dependent on the cell for survival and cannot exist outside of it. The phrasing "cannot survive outside the living cell" is misleading because it implies total independence, which is not accurate.

4. **Statement 4**: "Mitochondria divide by fission."
- This statement is **correct**. Mitochondria replicate through a process called binary fission, similar to bacterial division, which allows them to increase in number within the cell.

### Conclusion:
The incorrect statement is **Statement 3**.

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