The correct answer is option 1, 23°. The Earth rotates on its axis at an inclination of approximately 23°. This inclination is also known as the axial tilt or obliquity of the Earth. It is the reason we have seasons on Earth.

As the Earth orbits around the Sun, the tilt causes different parts of the Earth to receive varying amounts of sunlight throughout the year. When the northern hemisphere is tilted towards the Sun, it experiences summer, while the southern hemisphere experiences winter. In contrast, when the northern hemisphere is tilted away from the Sun, it experiences winter, while the southern hemisphere experiences summer. The equator, which is not tilted towards or away from the Sun, experiences relatively consistent temperatures throughout the year.

This axial tilt is also responsible for the length of daylight changing throughout the year, with longer days in summer and shorter days in winter.