O.P. of a solution can be measured by

Options

A. Photometer
B. Osmometer
C. Calorimeter
D. Plasmolysis

Answer

To solve the question "O.P. of a solution can be measured by", we will analyze each option provided and identify the correct one.

### Step-by-Step Solution:

1. **Understanding Osmotic Pressure (O.P.)**:
- Osmotic pressure is the pressure required to stop the flow of water across a semipermeable membrane due to osmosis. It is an important concept in biology, particularly in plant physiology.

**Hint**: Remember that osmotic pressure is related to the movement of water and solutes across membranes.

2. **Analyzing the Options**:
- **Option A: Photometer**:
- A photometer is used to measure the intensity of light. It does not measure osmotic pressure.

**Hint**: Think about what each instrument is specifically designed to measure.

- **Option B: Osmometer**:
- An osmometer is a device specifically designed to measure the osmotic strength or osmotic pressure of a solution. This makes it a suitable choice for our question.

**Hint**: Look for the device that directly relates to osmotic properties.

- **Option C: Calorimeter**:
- A calorimeter measures the heat involved in chemical reactions. It is not related to osmotic pressure.

**Hint**: Consider whether the device measures heat or osmotic properties.

- **Option D: Plasmolysis**:
- Plasmolysis refers to the process where the protoplasm of a cell shrinks away from the cell wall due to loss of water. While it is related to osmotic pressure, it is not a measuring device.

**Hint**: Determine whether the term refers to a process or a measurement tool.

3. **Conclusion**:
- After evaluating all the options, the correct answer is **Option B: Osmometer**. This device is specifically used to measure osmotic pressure.

### Final Answer:
The osmotic pressure (O.P.) of a solution can be measured by **option B: osmometer**.