The correct option is A Both assertion and reason are true and the reason is the correct explanation of assertion
Plants absorb carbon dioxide, which is a greenhouse gas, during photosynthesis, thereby reducing global warming. But, deforestation and the increase in greenhouse gases lead to global warming. Global warming can be controlled by adopting certain measures such as, reducing deforestation, planting more trees, cutting down use of fossil fuel, slowing down the growth of human population etc.
Therefore, both assertion and reason are true and reason is the correct explanation of assertion.