Questions

Excessive use of nitrate including manure may be responsible forthe presence of toxic substance in groundwater. Phosphate can also enter the groundwater via excessive use of fertilizers. High application rates of nitrogen containing fertilizers combined with the high-water solubility of nitrate, leads to increased runoff into surface water as well as leaching into groundwater, thereby causing groundwater pollution.

Only a fraction of the nitrogen-based fertilizers, is converted to produce and other plant matter. Nitrate pollution in groundwater comes from pit latrines, it can cause blue baby syndrome.

The alphabetical value of the letters in the left hand column follows through the sequence of Prime Numbers, with the letters in the right hand column representing the corresponding reverse alphabetical values. So,

M = Reverse of M = N.

The Right of Children to Free and Compulsory Education Act or Right to Education Act (RTE) which describes the importance of free and compulsory education for children between 6 and 14 in India is enacted under Article 21A of the Indian Constitution.

It is a Postbox or a Mailbox which contains thousands of letters or mails or messages.

The logic in the given puzzle is 

4 + 4 = 4 * 4+1 = 4 * 5 = 20

5 + 5 = 5 * 5+1 = 5 * 6 = 30

6 + 6 = 6 * 6+1 = 6 * 7 = 42

7 + 7 = 7 * 7+1 = 7 * 8 = 56

Similarly

9 + 9 = 9 * 9+1 = 9 * 10 = 90.

A magnetic domain is a region within a magnetic material in which the magnetization is in a uniform direction. This means that the individual magnetic moments of the atoms are aligned with one another and they point in the same direction.