Answer:
B. The particles are charged
Step-by-step explanation:
We know that a moving charge particle in magnetic field experiences a magnetic force given by :

In the context, a very hot gas of piatma consists of freely moving positive particles as well as negative particles. Now when the plasma is placed in the region of a magnetic field, then it experiences a force and thus it shows that the particles are charged particles.
Hence , option (B) is correct.