Questions

Covalent bonding occurs when pairs of electrons are shared by atoms. Atoms will covalently bond with other atoms in order to gain more stability, which is gained by forming a full electron shell. By sharing their outer most (valence) electrons, atoms can fill up their outer electron shell and gain stability.

Examples of compounds with covalent bonds ::

HCl, CO2, O2,... 

The 7th International Tourism Mart to be held in Tripura, the northeastern state in India for the first time for 3 days from Nov 22nd to Nov 24th.

In terms of concentration of impurity (a.k.a impurity doping concentration, often abbreviated to doping concentration), from the highest to the lowest among the three regions of a bipolar junction, emitter, collector, and base are the correct order. The above order is independent of the type of BJT, npn or pnp

It is due to the deficiency of Vitamin A. Retinol which is present in vitamin A. Its deficiency causes night blindness. It is available in carrots. 

REM sleep i.e, Rapid Eye Movement sleep is also known as paradoxical sleep because the measures of the brain activity closely resemble waking consciousness, but the person is incapable of moving as the brain is in fully active mode that time.