Answer:
a. The magnitude of the magnetic field is changing.
b. The magnetic field is changing direction with respect to the bracelet.
c. The bracelet is moving in the magnetic field.
Explanation:
Magnetic flux is a measure of the total magnetic field that passes through a given area. The value of the flux depends on the magnitude of the magnetic field, the area it crosses and its orientation relative to the magnetic field. Therefore, all three reasons are valid.