C1 REVISION TOPIC 1 The Earth’s atmosphere has changed over billions of years, but for the past 200 million years it has been much as it is today. We are, however, causing our atmosphere to change by human activity. Burning fossil fuels and deforestation are two examples of human effect on the environment. Composition of the Earth's atmosphere Air is made up of nitrogen (78%), oxygen (21%) and other gases (1%) The composition of air You need to know the proportions of the main gases in the atmosphere…
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