Questions

Phage typing is based on the fact that bacterial viruses attack specific cells. Phage typing is a method used for detecting single strains of bacteria. It is used to trace the source of outbreaks of infections. 

Nitrogen (N2) forms Three Covalent Bonds to become stable.

Here the Atmomic Number of Nitrogen is 7. Because there are 2 electrons in the first orbital and 5 in the second and you still have space for 3 more. So it shares, 3 to get the stable octet. Therefore, there are 3 covalent bonds in N2.

Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are low-pressure areas which, along with the anticyclones of high-pressure areas, drive the weather over much of the Earth.

Middle latitude cyclones are fueled by air high in the atmosphere.

True, the greenhouse effect is caused solely by human activities such as deforrestation, depletion of natural resources and emission of CO2 by using vehicles, refrigerators and AC's.

When an atom loses an electron it becomes a positive ion by acquiring negatively charged. When it loses electron, the atom's radius also decreased.