The Kirkwood Gaps (See Figure 8-11,Comins,Discovering the Essential Universe,6th Ed

The Kirkwood gaps (see Figure 8-11,Comins,Discovering the Essential Universe,6th ed.) are in the:

A) asteroid belt at places where there are very few asteroids.
B) rings of Saturn, where there is less material than at other radii.
C) spectrum of hydrogen gas, where light has been absorbed by molecules first identified by Kirkwood.
D) equatorial region of the Sun, where no sunspots are found.