An electron is moving with a speed of \[{{10}^{8}}\,m/\sec \] perpendicular to a uniform magnetic field of intensity B. Suddenly intensity of the magnetic field is reduced to B/2. The radius of the path becomes from the original value of r [MP PET 1993]

• A.            No change                            
• B.            Reduces to r / 2
• C.            Increases to 2r                    
• D.            Stops moving