a. A stationary c

a. A magnetic field exerts force only on moving charges. So, a stationary charge kept in a magnetic field does not experience any force until it starts moving.
b. The direction of force experienced by a current carrying conductor placed in a magnetic field depends on:

● the direction of the current in the conductor

● direction of the magnetic field applied

c. The force experienced by a current carrying conductor placed in a uniform magnetic field is maximum when the current makes right angle with the magnetic field.

d. The force experienced by a current carrying conductor placed in a uniform magnetic field is maximum when the current makes right angle with the magnetic field.