What describes a tic?

A tic is characterized by brief, repetitive, coordinated movements or vocalizations that occur at irregular intervals. This definition fits well with the nature of tics, which are typically sudden and can vary in intensity and frequency. They are often seen in disorders such as Tourette syndrome and can be motor (involving physical movements) or vocal (involving sounds).

The key aspects that highlight option B as the correct choice are the repetitive nature of the movements and the irregular intervals at which they occur, distinguishing tics from more continuous forms of movement or more severe involuntary muscle contractions.

The other options describe different types of movements that do not align with the defining features of tics. For example, involuntary movements associated with spasticity are usually more sustained rather than brief and repetitive, while slow, twisting movements are indicative of dystonic movements rather than tics. Rapid jerky movements affecting the face and arms may be part of other movement disorders but do not specifically fit the description of a tic, which should include the element of being precisely brief and repetitive.