The large gaps in the asteroid belt (often called the kirkwood gaps after the iu astronomer who discovered them) are caused by

a. tidal forces from jupiter
b. orbital resonances with jupiter
c. tidal forces from sun
d. the competing gravitational tugs of mars and jupiter

B. Orbital resonances with Jupiter

Explanation: Kirkwood gaps are gaps created by the inconistences in the number of asteroids in the main asteroid belts ,it is usually in fractions such as 1/2,2/3 of Jupiter's period.

These gaps were first observed in 1866 by Daniel Kirkwood, who also correctly described their origin in the orbital resonances with Jupiter.

The loss of objects from the Kirkwood gaps is due to the overlapping of the ν5 and ν6 secular resonances within the mean-motion resonances.

small = small current large mag large current

answer;

d. are made mostly of liquid

explanation;

-the general   composition and structure planets includes; they have a thick gas and liquid layer covering a small,solid core. mostly the gases are hydrogen and helium atmosphere and layers of liquid hydrogen. for instance neptune and uranus are examples of the outer planets, they have a core covered by ice and ammonia.

-neptune's atmosphere is hydrogen and helium with a bit of methane so there is no oxygen to breath and the interior is made up of frozen water and ammonia with a rock and iron core. thus, there is no liquid water or solid surface to survive.