How many of the following statements are incorrect ?
(i) The shape of the cell may vary with the function they perform.
(ii) Nerve cells are some of the longest cells.
(iii) The largest isolated single cell is the egg of an ostrich.
(iv) Blue-green algae are eukaryotes.
(v) Prokaryotic cells are generally smaller and multiply slowly than eukaryotic cells.

Options

A. Two
B. Four
C. Three
D. Five

Answer

To determine how many of the given statements are incorrect, we will analyze each statement one by one:

1. **Statement (i)**: The shape of the cell may vary with the function they perform.
- **Analysis**: This statement is correct. Cells can have different shapes based on their specific functions (e.g., nerve cells are long, while red blood cells are biconcave).

2. **Statement (ii)**: Nerve cells are some of the longest cells.
- **Analysis**: This statement is also correct. Neurons can extend over long distances, making them among the longest cells in the body.

3. **Statement (iii)**: The largest isolated single cell is the egg of an ostrich.
- **Analysis**: This statement is correct. The ostrich egg is indeed the largest single cell known.

4. **Statement (iv)**: Blue-green algae are eukaryotes.
- **Analysis**: This statement is incorrect. Blue-green algae, also known as cyanobacteria, are prokaryotes, not eukaryotes.

5. **Statement (v)**: Prokaryotic cells are generally smaller and multiply slowly than eukaryotic cells.
- **Analysis**: This statement is incorrect. While prokaryotic cells are generally smaller than eukaryotic cells, they typically multiply much faster than eukaryotic cells.

Now, let's summarize the findings:
- Correct statements: (i), (ii), (iii)
- Incorrect statements: (iv), (v)

**Total Incorrect Statements**: 2 (iv and v)

### Final Answer:
There are **2 incorrect statements**.