The length of time from sunrise to sunrise varies for multiple reasons:.1. Earth's varying distance from the Sun, 2. The varying speed with which the Earth moves in its orbit, and 3. The varying north/south position of the Sun. 4. To avoid these complications and make our lives simpler, our clocks use .

Earth's varying distance from the Sun,

Explanation:

There has been an established fact that the sunrise and sunset times varies because of the earth’s tilt in its orbit and its varying distance from the sun. At different locations on the earth, the times when the sun comes up and goes down would certainly be different on any given day. The north of Gisborne in New Zealand witnesses the world's first sunrise each and every day.

The correct option is 1 Earth's varying distance from the Sun.

Explanation:

As the orbit of Earth around the Sun is elliptical thus during the year time, the distance of Earth from the Sun varies as during the motion of Earth in a year. In this context as the distance between Earth and Sun changes, the Sunrise and Sunset times varies and thus the length of time between the Sunrise and Sunset also varies.