Air bubbles are dangerous to the patient because it causes air embolism. An embolism is an obstruction in a blood vessel due to a blood clot or other foreign matter that gets stuck while traveling through the bloodstream.

Ecology is the branch of biology dealing with the relations and interactions between organisms and their environment, including other organisms.

The Malthusian theory explains the relationship between the growth in food supply and in population. It states that population increases faster than food supply and if unchecked leads to vice or misery.

A progressive tax is one in which the tax rate increases as the amount being taxed increases. A progressive tax takes a higher percentage of tax from people with higher incomes. It means that the more a person earns, the higher his average rate of tax will be. Thus, it helps in reducing the economic inequalities in India.

Levee is a raised embankment along a watercourse which may occur naturally through sedimentation during overflow of the channel or may be man-made to prevent flooding. A levee is an embankment, like a dam, constructed to prevent the overflow of a body of water.

The tides in the seas of Earth are caused by the gravitational attraction of the Moon, and of the Sun. When the Sun and the Moon are both on the same side of the Earth, (i.e. New Moon) then the tides are of greatest amplitude. When these two bodies are on opposite sides of the earth (Full Moon) then the amplitude of the tides will be least.

The first printing press was brought by Portuguese missionaries in Goa.

Bhangar and Khadar are the types of alluvial soil. Bhangar is an old soil which consist kankar nodules in the sub soil with calcium carbonate. Khadar is a new alluvial soil and it is a most fertile soil than the Bhangar soil.

Buxa Tiger Reserve is located in the north-eastern corner of Jalpaiguri district, West Bengal. The Buxa Tiger Reserve was established in the year of 1982-83 to save one of the most endangered and beautiful animal species, The Royal Bengal Tiger. It is seriously threatened by the ongoing dolomite mining.

The Tehri Dam is the highest dam in India and one of the highest in the world. It is a multi-purpose rock and earth-fill embankment dam on the Bhagirathi River near Tehri in Uttarakhand, India.