Read the following
conductivity
excitability
contractibility
elasticity
all or none
How many properties are shown by nerve cell?

Options

A. (1) two
B. (2)Three
C. (3) four
D. (4) five

Answer

To determine how many properties are shown by nerve cells from the given list (conductivity, excitability, contractibility, elasticity, all or none), we can analyze each property step by step.

### Step-by-Step Solution:

1. **Identify Nerve Cells**:
- Nerve cells, also known as neurons, are specialized cells that transmit information throughout the body. They are primarily found in the central nervous system.

**Hint**: Remember that nerve cells are crucial for communication in the body.

2. **Evaluate Conductivity**:
- Conductivity refers to the ability of nerve cells to transmit electrical signals. When a nerve cell is stimulated, it generates an electrical impulse that travels along its length and can be transmitted to other cells.

**Hint**: Think about how signals are passed along nerves.

3. **Evaluate Excitability**:
- Excitability is the ability of nerve cells to respond to stimuli. At rest, the inside of a neuron is negatively charged compared to the outside. When stimulated, the charge changes, allowing the nerve cell to fire and transmit signals.

**Hint**: Consider how nerve cells react to changes in their environment.

4. **Evaluate Contractibility**:
- Contractibility is the ability to shorten and generate force, which is a property of muscle cells, not nerve cells. Nerve cells do not contract.

**Hint**: Recall that muscle cells are responsible for movement, not nerve cells.

5. **Evaluate Elasticity**:
- Elasticity is the ability to return to original shape after being stretched or compressed, which is also not a property of nerve cells. This property is more relevant to connective tissues.

**Hint**: Think about which types of cells can stretch and return to form.

6. **Evaluate "All or None"**:
- The "all or none" principle refers to the fact that once a nerve cell is stimulated past a certain threshold, it will fire completely or not at all. This is a characteristic of nerve cells.

**Hint**: Consider how nerve impulses work in a binary manner.

### Conclusion:
From the analysis, nerve cells exhibit the following properties:
- **Conductivity**: Yes
- **Excitability**: Yes
- **Contractibility**: No
- **Elasticity**: No
- **All or None**: Yes (in terms of firing)

Thus, the properties shown by nerve cells are **3**: conductivity, excitability, and the all or none principle.

### Final Answer:
Nerve cells show **3 properties** from the given list.