The summer season is closely linked to which of the following a) an equinox because the earth is very close to the sun b) an equinox because the earth is very far away from the sun c) a solstice because the earth is very close to the sun d) a solstice because the earth is far away from the sun

Correct C). A solstice because the earth is very close to the sun  

In the summer days are longer because the sun rises early and sets late in the night. When the north pole of the earth is tilted toward the side of the sun, northern hemisphere receives more sunlight and it is summer on the northern hemisphere. As the earth keeps rotating on its orbit the tilt of north pole changes. and when it is away from the sun, it is winter in the northern hemisphere.

The day when the earth's north pole is close to the sun is called summer solstice, and this seems to be the longest day on the northern hemisphere.