The correct answer is option 'C' - Electrostatic type.

Explanation:

1. Introduction:
Voltmeters are instruments used to measure voltage or potential difference across a circuit. Different types of voltmeters are available, each with its own characteristics and power consumption levels.

2. Power Consumption:
Power consumption refers to the amount of electrical power utilized by a device. In the context of voltmeters, power consumption is related to the amount of energy required to operate the instrument.

3. Types of Voltmeters:
a) Induction type: Induction type voltmeters work based on the principle of electromagnetic induction. They consist of a coil and a movable conductor. These voltmeters have relatively high power consumption due to the electromagnetic forces involved.

b) Hot wire type: Hot wire type voltmeters operate by measuring the change in resistance of a wire due to the current passing through it. These instruments consume a moderate amount of power.

c) Electrostatic type: Electrostatic type voltmeters utilize the principle of electrostatic attraction between charged plates. They consist of stationary and movable capacitive plates. This type of voltmeter has the least power consumption among the given options.

d) Moving iron attraction type: Moving iron attraction type voltmeters work based on the principle of attraction between a fixed and a movable iron piece due to the magnetic field produced by the current. These voltmeters have relatively higher power consumption compared to the electrostatic type.

4. Reasoning:
The electrostatic type voltmeter has the least power consumption among the given options because it operates based on the electrostatic attraction between charged plates. This mechanism does not require significant energy consumption, resulting in lower power requirements.

In contrast, the other types such as induction type, hot wire type, and moving iron attraction type voltmeters involve electromagnetic or magnetic forces, which require higher power consumption to operate.

Therefore, the electrostatic type voltmeter is the most energy-efficient option among the given choices, making it the voltmeter with the least power consumption.