While Installing a Cylinder Head, Technician a Says the Threads

While installing a cylinder head, technician A says the threads in cylinder head bolts must be lubricated before installation. Technician B says that only the underside of the bolt head requires lubrication and that the threads only need be clean. Who is correct?

A) Technician A
B) Technician B
C) Both A and B
D) Neither A nor B