Answer: A)
B) X: Back of hand, for force
Y: Thumb, for velocity
Z: Palm of hand, for force
Explanation:
Right-hand rule is used to find direction of magnetic force. When a charge enters magnetic field, magnetic force acts perpendicular to both magnetic field and velocity of charged particle and the charge moves in a curved path.
F = q v × B
The direction of the magnetic force is given by the right hand:
The fingers should be point in the direction of the magnetic field. Then the direction of palm gives the direction of magnetic force acting on positive charge and back of hand gives direction for magnetic force for negative charge.