Option 1: The South Pole experiences 24 hours of darkness.

This statement is incorrect. The South Pole experiences 24 hours of daylight during the winter solstice, not darkness. This is because during this time, the South Pole is tilted towards the Sun.

Option 2: It occurs on June 21.

This statement is incorrect. The winter solstice actually occurs on December 21 in the Northern Hemisphere. In the Southern Hemisphere, it occurs on June 21.

Option 3: The North Pole experiences 24 hours of darkness.

This statement is correct. During the winter solstice in the Northern Hemisphere, the North Pole experiences 24 hours of darkness. This is because the Earth is tilted away from the Sun, causing the North Pole to be in constant shadow.

Option 4: The Sun is at aphelion.

This statement is unrelated to the winter solstice. Aphelion refers to the point in the Earth`s orbit when it is farthest from the Sun. The winter solstice is related to the tilt of the Earth`s axis, not its distance from the Sun.

Therefore, the correct option is option 3.