[Q]: Which best explains the importance of nitrogen in the cycling of energy and matter?
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OPTIONS:
- Nitrogen increases protein production in plants.
- Nitrogen decreases protein production in plants.
- Nitrogen decreases the effectiveness of photosynthesis.
- Nitrogen increases the effectiveness of photosynthesis.
****
[A]: Nitrogen increases protein production in plants.

[Q]: Earth rotates on its north-south axis. Which statement best describes one complete rotation?
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OPTIONS:
- It takes six months and causes summer and winter seasons.
- It takes 24 hours and causes night and day.
- It takes 29 days, which represents one cycle of the Moon's phases.
- It takes 365 days, which represents one Earth year.
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[A]: It takes 24 hours and causes night and day.

[Q]: The pull of gravity on Earth is a direct result of the
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OPTIONS:
- mass of Earth.
- magnetic field of Earth.
- rotation of Earth on its axis.
- weight of Earth's atmosphere.
****
[A]:
mass of Earth.