- Nitrogen and oxygen (A) are diatomic molecules and are poor absorbers of both incoming solar (shortwave) and outgoing Earth (longwave) radiation, explaining why they are not greenhouse gases. - The atmospheric window (C) is a range of wavelengths (roughly 8-13 µm) in the infrared spectrum where the atmosphere, particularly water vapour and CO2, is relatively transparent, allowing some Earth radiation to escape to space. - A large proportion of atmospheric radiant energy, absorbed from the Earth's surface, is indeed re-emitted downwards as back radiation (D), contributing significantly to surface warming via the greenhouse effect. While the exact percentage can vary, the concept that a large amount is directed back is correct.