Two technicians are discussing metric bolts. Technician A says that the letter M on a bolt head specifies a metric bolt followed by the diameter in millimeters (mm). Technician B says that P stands for the thread pitch and that D stands for the size of the bolt head across the flats. Who is correct? A. Technician A only B. Both Technicians A and B C. Technician B only D. Neither Technician A nor B