Answer:
This is the first answer,
winter solstice
The winter solstice occurs during the hemisphere's winter. In the Northern Hemisphere, this is the December solstice (usually December 21 or 22) and in the Southern Hemisphere, this is the June solstice (usually June 20 or 21).
and this is the second one,
the tilt of the Earth on its axis
Seasons change because of the tilt of the Earth and the planet's movement around the Sun. Did you know? It takes about 365.25 days for the Earth to orbit the Sun. We have leap years to make up for the extra ¼ day!
I’m not good at this but I’m guessing it’ll be the first one!
Niels Bohr is the first person to describe a chemical reaction as the combination of atoms.