1.1 The southern hemisphere is experiencing summer.
1.2 The diagram shows this because the rays of the sun are directly overhead the Tropic of Capricorn (23.5°S), which is the southernmost point at which the sun's rays can be directly overhead. This is also evident from the fact that the Antarctic Circle (66.5°S) is experiencing 24 hours of daylight, which only happens during the southern hemisphere summer.
2. The part of the Earth's surface that has 24 hours of daylight is the South Pole (90°S) on December 22 or 23, which is the summer solstice in the southern hemisphere.
3. This diagram likely represents either the December solstice (around December 21 or 22) or the June solstice (around June 20 or 21), as these are the times when the sun's rays are most directly overhead the Tropics of Capricorn and Cancer, respectively.
4. The two factors that cause the Earth to have seasons are the tilt of the Earth's axis and its revolution around the sun. The tilt of the Earth's axis (about 23.5 degrees) causes different parts of the Earth to be tilted toward or away from the sun at different times of the year, resulting in the changing seasons. The Earth's revolution around the sun also affects the seasons, as it causes the Earth to be closer or farther away from the sun at different times of the year, although this effect is relatively small compared to the tilt of the axis.