Question

1$hp$ is equal to
$\begin{aligned} & \text{A}\text{. }0.746kW \\\ & \text{B}\text{. }7.46kW \\\ & \text{C}\text{. }74.6kW \\\ & \text{D}\text{. }746kW \\\ \end{aligned}$

Answer 1

Horsepower is a unit of power. Or the rate at which the work is done. Horsepower refers to the output power of an engine or motor. Horsepower term was coined by James watt. Horsepower term was coined to compare the power output of a horse with an engine. The unit of power watt is too small so we use bigger units of power which is kilowatt and horsepower.

Complete answer:
Power is defined as the rate of doing work. If an agent does an work $W$in time $t$ then its average power is given by
${{P}_{av}}=\dfrac{W}{t}$
So the shorter is the time taken by a person or a machine in performing a particular task , the larger is the power of that person or machine .
The SI unit of power is watt. The power of an agent is one watt if it does work at the rate of one joule per one second.
The bigger unit of power is horsepower. One horsepower is $746\text{ Watt}$ which is equals to $0.746kW$ because $1W={{10}^{-3}}kW$

So option A is correct.

Additional Information:
Power is the ability of doing work. Unit of power is Watt. So one watt is the power when one joule of work is done in one second. The unit watt is very small. So in actual practice we use kilowatt which is equal to $1000$ watts. Horsepower term invented to compare the output of an engine with the output of a horse.

Note:
Power is a scalar quantity because it is a ratio of two scalar quantity work and time. We use kilowatt hour as a unit for electrical energy usage. Kilowatt-hour is also known as a board-of-trade unit. It is the commercial unit of electrical energy. One kilowatt hour is the electrical energy consumed by an appliance of one-kilowatt in one hour.
$1kWh=1kW\times 1h=1000W\times 3600s=3.6\times {{10}^{6}}J$.