is still likely to distract your attention from the road
While driving your concentration is required all the time. Even using a hands-free kit can still distract your attention from the road. Any distraction, however brief, is potentially dangerous and could cause you to lose control. Except in a genuine emergency, it is an offence to use a hand-held phone while driving.
B is acceptable in a vehicle with power steering
C will significantly reduce your field of vision
D will affect your vehicle's electronic systems