The correct answer is option 'D': Summer Solstice.

Explanation:

Summer Solstice is the day when the sun reaches its highest position in the sky and appears to stand still for a moment before starting its descent. This day marks the longest day of the year, with the most amount of daylight hours.

The Summer Solstice occurs around June 21st in the Northern Hemisphere and December 21st in the Southern Hemisphere. It is one of the four major events that mark the changing of the seasons, which are known as solstices and equinoxes.

The Summer Solstice is caused by the tilt of the Earth's axis. During the summer months, the Northern Hemisphere is tilted towards the sun, which causes the sun's rays to be more direct and intense. This results in longer daylight hours and warmer temperatures.

On the day of the Summer Solstice, the sun appears to stand still in the sky before starting its descent towards the horizon. This phenomenon is known as the solstice, which comes from the Latin words sol (sun) and sistere (to stand still).

Conclusion:

In conclusion, the correct answer to the question is option 'D': Summer Solstice. This day marks the longest day of the year, with the most amount of daylight hours, and is caused by the tilt of the Earth's axis. Understanding the solstices and equinoxes is important for understanding the changing of the seasons and the patterns of the natural world.

On 21st June the sun is directly over the tropic of cancer which is called summer solstice.on this day we have longest day and shortest night..