What Causes a Glitch in the Rotation Rate of a Pulsar

What causes a glitch in the rotation rate of a pulsar?

A) Hot spots develop on the surface of a neutron star, and from these spots jets of material can suddenly shoot out causing a minor but abrupt chance in the rotation rate.
B) Because of their enormous density, the rotation rates of neutron stars are quantized and must change abruptly from one rotation rate to another.
C) As the star slows, its shape becomes more spherical. If its rotation rate adjusts to this suddenly, a glitch occurs.
D) When a pulsar occurs in a binary system, the binary companion can send clumps of material to land on its surface. This will change its rotation rate abruptly.