Questions: The warmer weather of summer in many parts of the Northern Hemisphere is caused by the fact that during this period - this area is closer to the Sun than at other times. the Sun emits the greatest amount of energy. the melting of ice raises the sea level in this area. this area receives more direct sunlight.

The answer is the fourth one: this area receives more direct sunlight.

Explanation for each option:

1. This area is closer to the Sun than at other times: This is incorrect. The Earth's distance from the Sun does not significantly change enough to cause the seasons. The Earth's orbit is nearly circular, so the distance variation is minimal.
2. The Sun emits the greatest amount of energy: This is incorrect. The Sun's energy output remains relatively constant over the course of a year.
3. The melting of ice raises the sea level in this area: This is incorrect. While melting ice can affect sea levels, it does not directly cause warmer weather.
4. This area receives more direct sunlight: This is correct. During summer in the Northern Hemisphere, the tilt of the Earth's axis causes this region to receive more direct sunlight, leading to warmer temperatures.

Summary: The warmer weather of summer in many parts of the Northern Hemisphere is caused by the fact that this area receives more direct sunlight.