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.

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