Regarding the assertion and reason, choose the correct option.
Assertion [A]: Greenhouse effect is due to a thick layer of CO2.
Reason [R]: The glass panels of a greenhouse allow the sunlight to filter through but prevent heat from being re-radiated into outer space.
A greenhouse stays warm inside, even during winter. Sunlight shines in and warms the plants and air inside. But the heat trapped by the glass cannot escape out. CO2 in the troposphere behaves like the glass panels of a greenhouse allowing the sunlight to filter through, but preventing the heat from being re-radiated into outer space. This is called the greenhouse effect. During the day, the sun shines through the atmosphere. Earth's surface warms up in the sunlight. At night, Earth's surface cools, releasing the heat back into the air. But some of the heat is trapped by the greenhouse gases (especially carbon dioxide and water vapour) which prevent the heat from escaping into outer space and hence, the warmth of Earth is maintained.