Questions

A primary key is a special relational database table column or combination of columns designated to uniquely identify all table records. That is, A primary key is a column or set of columns in a table that uniquely identifies tuples (rows) in that table.

A primary key, also called a Primary Keyword.

Main Features Primary key are ::

It must contain a unique value for each row of data.

It cannot contain null values.

A Windmill.

Skimming is the removal of any material or particles that are floating on the surface. Hence, Removal of oil and grease from sewage - waste water is called as skimming.

Aluminum has a resistivity varying from 2.65 to 2.82 × 10−8 Ω m.The resistivity of copper is generally given as: 1.72 x 10-8 Ω.m.So, since resistivity of aluminium is higher than that of copper, so Power dissipated will be greater than P. this is because rest of the factors (l, A and i) are constant.

Anarchy means Absence of government.

Process by which sediment is removed from its source is called Erosion.

Permanent hardness of water may be removed by the addition of Sodium Carbonate.

In all the given options, molecules are containing nonpolar covalent bonds.