Which of these gases is found in the lower layers of the atmosphere?

1. helium
2. hydrogen
3. neon
4. oxygen

What is the lower part of the thermosphere called?

1. troposphere
2. ionosphere
3. exosphere
4. mesosphere

Which of these activities do not produce greenhouse gases?

1. energy use
2. agriculture
3. afforestation
4. industrial process

Which of these gases is responsible for the depletion of the ozone layer?

1. argon
2. methane
3. water vapour
4. chlorofluorocarbons