The correct option is A Greenhouse effect
∙ Greenhouse effect is a process caused due to increase in the amount of gases such as carbon dioxide in the air. These gases trap the heat from the sun and cause a gradual rise in the temperature of the Earth's atmosphere.
∙ When the sun's energy reaches the Earth's atmosphere, some of it is reflected back but the rest is trapped in the Earth's atmosphere by greenhouse gases like carbon dioxide, methane, water vapour, etc.