**Anemometer: Measuring Wind Speed**

An anemometer is an instrument used to measure the speed of wind. It is designed to capture the kinetic energy of moving air and convert it into a measurable quantity. The correct answer to the question is option 'D', which states that an anemometer is most similar to a speedometer.

**Explanation:**

**1. Functionality**
- An anemometer measures the speed of wind by capturing the force exerted by the moving air.
- Similarly, a speedometer measures the speed of a vehicle by capturing the force exerted by the moving wheels.

**2. Measurement**
- An anemometer measures the speed of wind in units such as meters per second (m/s), kilometers per hour (km/h), or miles per hour (mph).
- A speedometer measures the speed of a vehicle in units such as kilometers per hour (km/h) or miles per hour (mph).

**3. Mechanical Design**
- An anemometer typically consists of three or four cups mounted on a horizontal axis, which rotate when exposed to wind. The rotation speed of the cups is directly proportional to the wind speed.
- A speedometer in a vehicle consists of a rotating magnet that interacts with a metallic cup attached to the speedometer cable. The rotation speed of the magnet is directly proportional to the vehicle's speed.

**4. Display**
- An anemometer may have a digital or analog display to show the measured wind speed.
- A speedometer in a vehicle usually has an analog display with a needle indicating the speed.

**5. Usage**
- Anemometers are commonly used in meteorology, aviation, and environmental monitoring to measure wind speed.
- Speedometers are an essential part of vehicles, providing real-time information about the vehicle's speed.

**Conclusion:**
An anemometer and a speedometer are similar instruments in terms of functionality, measurement, mechanical design, display, and usage. Both instruments capture the force exerted by moving objects (wind or wheels) and provide a measurement of their speed. Therefore, the correct answer is option 'D' - speedometer.