Verified answer

Answer:

A. Hour

Step-by-step explanation:

Earth's rotation is the spin or the planet's rotation around its axis. This rotation is remnant of the momentum that created the solar system. The time it takes for Earth, or any other planet, to complete its spin around its access is best measured by hours. With the case of the planet Earth, the planet spins or rotates once every 24 hours with respect to the sun. One full rotation of the Earth around its axis constitutes an entire day.

Measuring rotation using the other means provided are cumbersome and impractical.

• Millennium: There are 0.000003 millennium
• Seconds: 86400 seconds
• Year: 0.00273973 years

As shown here, hours is still the measuring unit is best used to describe the duration of the earth's rotation.

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