1. Which one of these processes increases carbon dioxide levels?
- Nitrogen Fixation
- Volcanic Activity
- Dissolution in the oceans
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2. Why does the rate of photosynthesis increase in the summer?
- Shorter day hours and decreased rainfall
- Longer day hours and hotter weather
- Longer day hours and increased rainfall
- Shorter day hours and hotter weather
3. What percentage, on average, of the air is nitrogen?
4. Why has the percentage of oxygen increased from the early atmosphere to now?
- Volcanic eruptions
- The photosynthesis of plants
- Human respiration
- The activity of bacteria
5. Why has the percentage of hydrogen decreased from the early atmosphere to now?
- It has been trapped underground
- Human activity
- It's escaped from the atompshere
- It dissolved in oceans and rivers