B Christmas is celebrated in summer due to the rotation of the earth.

b Rotation of the Earth:
The rotation of the Earth is the spinning of the Earth on its axis, which takes approximately 24 hours to complete. This rotation causes day and night. As the Earth rotates, different parts of the Earth receive different amounts of sunlight.

b Seasons:
The change in seasons is primarily caused by the tilt of the Earth's axis. The Earth's axis is tilted at an angle of about 23.5 degrees relative to its orbit around the Sun. This tilt results in different parts of the Earth receiving different amounts of sunlight at different times of the year. As a result, we experience four seasons - spring, summer, autumn, and winter.

b Revolution of the Earth:
The revolution of the Earth refers to its orbit around the Sun. It takes approximately 365.25 days for the Earth to complete one revolution around the Sun. This revolution, along with the tilt of the Earth's axis, is responsible for the change in seasons.

b Christmas in the Northern Hemisphere:
In the Northern Hemisphere, where Christmas is celebrated, the tilt of the Earth's axis means that during the month of December, the Northern Hemisphere is tilted away from the Sun. This results in shorter days and longer nights, as the Sun is lower in the sky and its rays are spread out over a larger area.

b Christmas in the Southern Hemisphere:
In the Southern Hemisphere, the tilt of the Earth's axis means that during the month of December, the Southern Hemisphere is tilted towards the Sun. This results in longer days and shorter nights, as the Sun is higher in the sky and its rays are more concentrated.

b Conclusion:
Christmas is celebrated in summer in the Southern Hemisphere because during the month of December, the Southern Hemisphere experiences summer due to the tilt of the Earth's axis. The rotation of the Earth also plays a role in the length of daylight and darkness experienced during this time.