Questions

1.Logout of your computer each time you have finished using it

2.Install and use anti-virus software on your computer 

3.Do not use emails on your machine

4.Make sure all your files are safely stored to your floppy disks

As there is no atmosphere surrounding the moon, the second from any band that is played there cannot travel outwards there is no material medium surrounding if for its propagation.

Gear finishing operation is called Burnishing.

Biodegradable substances can be broken down into simpler, harmless substances in nature with due course of time by the biological process such as action of microbes. They can be recycled as a part of food chain.

Here, Leather bags are biodegradable.

The part of the earth and its atmosphere in which living organisms exist or that is capable of supporting life is called Biosphere.

River.

It always runs  or flows but never walks.

It will sound like murmuring but never talks.

It has bed but never sleeps.

It has mouth but never eats.

The main group number for an element can be found from its column on the periodic table. For example, carbon is in group 4 and has 4 valence electrons. Oxygen is in group 6 and has 6 valence electrons.