The correct answer is: D. both (a) and (b)
The Earth rotates on its axis once every 24 hours, which is why we have day and night. The Earth also revolves around the Sun once every 365.25 days, which is why we have seasons. The Earth’s axis is tilted at an angle of 23.5 degrees relative to its orbital plane. This tilt causes the Sun’s rays to hit different parts of the Earth more directly at different times of the year, which is why we have different seasons.
The variation in the duration of the day and the night is due to both the Earth’s rotation on its axis and its revolution around the Sun. During the summer, the Northern Hemisphere is tilted towards the Sun, so the Sun’s rays hit the Northern Hemisphere more directly. This makes the days longer and the nights shorter in the Northern Hemisphere. During the winter, the Northern Hemisphere is tilted away from the Sun, so the Sun’s rays hit the Northern Hemisphere less directly. This makes the days shorter and the nights longer in the Northern Hemisphere.
The Earth’s rotation on its axis causes the Sun to appear to move across the sky from east to west. The Earth’s revolution around the Sun causes the Sun to appear to move across the sky from south to north in the Northern Hemisphere during the summer and from north to south in the Northern Hemisphere during the winter.
The Earth’s tilt causes the Sun’s rays to hit different parts of the Earth more directly at different times of the year. This is why we have different seasons.