Which of the following options is NOT one of the meanings of the homonym 'register'?

Correct option is C

Option (c) is not a meaning of register.
· (a) “to show/express on the face” is valid: e.g., His shock registered on his face.
· (b) “to enroll/sign up” is valid: e.g., She registered for the seminar.
· (d) “a machine used to record sales” is valid: cash register.
· (c) is incorrect because in music, register refers to the range of pitches of a voice or instrument—not to a medieval instrument itself (often confused with “regal,” a small medieval keyboard instrument).
· Information booster: As a homonym, register works as both verb (to record; to show; to enroll) and noun (official list; tonal range in music; device like a register for ventilation or a cash register).