Hello there!
The only one i can see caused primarily by human activities would be A. Air Pollution.
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I think the answer would be c
The sun appears to cross the plane of Earth's equator
when it reaches either one of the "equinox" points in the sky.
At those times, the lengths of day and night are nominally equal
everywhere (except at the poles), and the occasions are marked
as the beginning of Spring and Autumn.
