Consider the following which can be found in the ambient atmosphere : 1. Soot 2. Sulphur hexafluoride 3. Water vapour Which of the above contribute to the warming up of the atmosphere ?

1. The question asks which substances found in the ambient atmosphere contribute to its warming up (i.e., act as greenhouse gases or influence the greenhouse effect). 2. Item 1: Soot (Black Carbon). Soot particles absorb solar radiation directly, heating the atmosphere. They also reduce the reflectivity (albedo) of snow and ice when deposited, leading to more absorption and warming. Soot contributes to warming. 3. Item 2: Sulphur hexafluoride ($SF_6$). This is a potent synthetic greenhouse gas with a very high global warming potential, although present in very small concentrations. It contributes to warming. 4. Item 3: Water vapour ($H_2O$). Water vapour is the most abundant and significant natural greenhouse gas in the Earth's atmosphere, playing a crucial role in trapping heat and regulating temperature. It contributes significantly to warming. 5. Since Soot, Sulphur hexafluoride, and Water vapour all contribute to the warming of the atmosphere in different ways, the correct answer is (D) 1, 2 and 3.