Questions

A greenhouse gas is a gas in an atmosphere that absorbs and emits radiant energy within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. 

Carbon dioxide is a main greenhouse gas, found in car exhaust pipes.
Methane and nitrous oxide is another type of greenhouse gas.

Oxygen is the only clean gas out there because we need it to survive. Therefore, the only gas that is not a greenhouse gas is Oxygen.

A metaphor is a figure of speech that is used to make a comparison between two things that aren't alike but do have something in common.

In all the given options we have Metaphors.

Normality is a way of expressing concentration of a solution and can be calculated by the formula-

Normality (N) = No. of gram equivalent of solute/ volume of solution (in litre)

Gram equivalent weight of H2 SO4 = Molecular weight/ No. of Hydrogen atom = 98/2 = 49 gm

No. of gram equivalent in 49 gm of H2 SO4 = 1

So, Normality in 1 litre of solution = 1/1 = 1 N

Double Vision

One of the most important result of the French Revolution was that Political power shifted to the bourgeoisie (Middle class people).

The Great French Revolution of 1789 not only overthrew the monarchy in France, but ultimately led to the destruction of the Old Order across Europe.

Prior to the French Revolution, the bourgeoisie or middle class, belonged to the Third Estate, which had the largest tax burden and virtually no rights.

The bourgeoisie gained an enormous amount of political power when the National Assembly issued the Declaration of the Rights of Man, and drafted a new constitution for France.