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.

It provides a framework for discussing network operations and design

Numismatics is the study or collection of currency, including coins, tokens, paper money, and related objects.

Town planning, Drainage system and Use of Bronze are the features of Indus Valley Civilization. Use of Iron was not the feature of this.

Biodegradable substances can be broken down into simpler, harmless substances in nature with due course of time by the biological process such as action of microbes. They can be recycled as a part of food chain.

Here, Leather bags are biodegradable.

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.