Questions

1.Hardware abstraction layer

2.Kernel

3.Subsystems

4.System Services.

The Length of the Day is determined in Astronomical Units.

The length of a day corresponds to the time the Earth takes to turn around on its axis, which is approximately 24 hours. But it's not exactly 24 hours. 

This phenomenon is due to tides raised by the Moon which slow Earth's rotation. Because of the way the second is defined, the mean length of a day is now about 86 400.002 seconds, and is increasing by about 1.7 milliseconds per century.

A metalloid is an element with properties between metals and non metals or the mix of both.

The six metalloids are arsenic, silicon, germanium, boron, antimony and tellurium.

Hence, silicon is the only metalloid in the given list.

Evaporation is the process that allows water to enter into the atmosphere.

Sunlight turns liquid water into water vapor which then rises higher into the atmosphere and forms into clouds.

Plants, too, help water get into the atmosphere through a process called transpiration.