A cylindrical bar magnet is rotated about its axis (Figure). A wire is connect from the axis and is made to touch the cylindrical surface through a contact. Then
A. a direct current is flows in the ammeter A
B. no current flows through the ammeter A
C. an alternating sunusoidal current flows through the ammeter A with a time period `T = 2 pi//omega`
D. a time varying non-sinosoidal current flows through the ammeter A
