The correct answer is (a) and (b) Explanation & Key Takeaways: • Carbon dioxide:- • A greenhouse gas- has become a major concern as climate change becomes a bigger issue. • The biggest culprit of carbon dioxide emissions for these countries is electricity- notably, burning coal. • It absorbs a part of terrestrial radiation and reflects back some part of it towards the earth’s surface. It is largely responsible for the greenhouse effect. • Its concentration is greater close to the earth’s surface as it is denser than air. • India is the fourth highest emitter of carbon dioxide in the world, accounting for 7 per cent of global emissions in 2017. • India’s CO2 emissions grew by an estimated 4.6% in 2017, despite a turbulent year for its economy. • China is the world's largest contributing country to carbon dioxide emissions. • The top four emitters in 2017, which covered 58 per cent of global emissions were China, the USA, the European Union and India. • Hence statements (a) and (b) are correct while statement (c) is incorrect.