Questions

United State Library of Congress, Washington D.C.

The American noncommissioned officer tradition began with creation of the Continental Army in 1775 at the beginning of the American Revolution. They adopted NCO traditions from French NCO.

The Chinese writers mention India by the name of "Yin-tu".

A method for providing fault tolerance by using multiple hard disk drives

It is ABACUS.

Words formed are as below 

BUS
CAB
CUB
US

Nitrogen is found as a diatomic molecule (N2) in nature. There is a triple bond between the two nitrogen atoms.

The triple bond is pretty strong. Therefore, it needs a lot of energy to break those bonds and participate in a reaction. So nitrogen is commonly referred to as and used as an inert gas (high abundance & low cost.) However, it’s not truly inert like most noble gases. Nitrogen does react if the conditions are met. But those conditions are not exactly mild, but are not as extreme as for noble gases.

It forms nitric oxide and nitrogen dioxide with oxygen, ammonia with hydrogen, and nitrogen sulfide with sulfur.