I believe the correct answer is A) parsec
Probably a small group of researchers because the climate is very harsh.
Seasonal changes refer for example to the fact that in the Norther hemisphere it's colder in December than in June. This is because the Earth's axis is tilted in a way that brings the Western Hemisphere closer to the sun in July and further from the Sun in December.
The correct answer is: Earth is tilt.
Factory smokestacks can produce greenhouse gases. Basically, carbon dixoide is the main source of greenhouse gases. But, it occurs natually from things such as volcanos.
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