What is the domain of the relation graph below?

Look at the picture.

Domain: -4 ≤ x ≤ 4

Range: -1 ≤ y ≤ 1

During the equinox, which happens in spring and fall, the earth tilts to give the equator the most direct sun. During the winter solstice, the Southern Hemisphere is tilted most toward the sun. The closer we get to Dec. 21, the shorter the days will get, but after that, the days will gradually get longer again.

Explanation: