Answer:
(C) Winter solstice
Explanation:
Sydney, and all of Australia, are located in the Southern Hemisphere. This means that the changes in the seasons and the position of the sun on the sky for that matter are the opposite of the ones in the Northern Hemisphere. The summer period in the Southern Hemisphere starts on December 21st, unlike the Northern Hemisphere where it starts on June 21. The reason why the summer starts n this date is because in this period the Southern Hemisphere is more exposed to the sun, as the Earth is tilted with its southern half towards it. This resulted in higher exposure to the sun, increased temperatures because of it, and the sun being the highest on the sky during the winter solstice. On the other hand, the sun will be the lowest on the sky during the summer solstice, as the Southern Hemisphere is tilted away from the sun during that period.
