Why was the term "Greenhouse" used? Explain.

Greenhouse effect is primarily due to the presence of:

If there were no $CO_2$ in the Earth's atmosphere,the temperature of the Earth's surface would be ..........

Which two gases contribute the most to the greenhouse effect?

The increase in temperature due to the trapping of energy by ozone,$CO_2$,and water vapour is known as:

The given diagram represents the greenhouse effect.
$I.$ Greenhouse gases absorb infrared radiation from the earth. The absorbed radiations are again emitted towards the earth's surface,heating it up.
$II.$ $CO_{2}, CH_{4}, CFCs$ and $N_{2}O$ are the gases responsible for the greenhouse effect.
$III.$ An increase in the level of greenhouse gases results in considerable heating of the earth,leading to global warming.
Which of the statements given above are correct?