A particle of charge q and mass m is moving with a velocity −vi^ ( v=0 ) towards a large screen placed in the Y−Z plane at a distance d. If there is a magnetic field B=B0k^, the minimum value of v for which the particle will not hit the screen is:
a. 3mqdB0
b. m2qdB0
c. mqdB0
d. 2mqdB0