The empty space between the Saturn rings is called________________
(A) The interplanetary space
(B) Zones
(C) Belts
(D) Cassini division

Hint
Saturn is the sixth planet in the solar system when counted from the sun. It is a gas giant planet and the radius of Saturn is nearly nine times that of the earth. The planet Saturn has rings around which are composed of fragments of comets, asteroids etc which failed to reach the planet surface. To answer this question, we need to analyse all the options given and select the correct one which indicates the empty space between the Saturn rings.

Complete step by step answer
Interplanetary space, also known as the interplanetary medium is the region of space within the solar system. In this space, all the members of the solar system move. But, it is just not the space between the rings of the Saturn, but the whole of the space which fills the solar system. So, option A is incorrect.
Zones and belts basically refer to the bands on the surface of Jupiter, or of Saturn.
In Jupiter, the bands are alternate in colour. The bands which are dark are known as belts, and the lighter bands are known as zones.
While in the case of Saturn, the striped cloud bands are divided into zones and belts.
 Thus, the zones and belts have nothing to do with the rings of the Saturn planet.
So, option B and C are incorrect. Since the only option left is option D.
Hence, the correct answer is option D, Cassini division.

Note
The rings of Saturn have gaps in between, which are of various sizes. These are created due to the gravitational pull of Saturn's moons on the tiny particles of its rings. The largest gap between the Saturn rings is called the Cassini division. It is a region with a width of 4800 km. It is the space between two particular rings of Saturn, known as A ring and B ring. It was discovered by Giovanni Cassini, hence the name Cassini division.