A metal rod of length l cuts across a uniform magnetic field B with a velocity v. If the resistance of the circuit of which the rod forms a part is r, then the force required to move the rod is

Options

A. `(B^(2)l^(2)v)/(r )`
B. `(Blv)/( r)`
C. `(B^(2)lv)/(r )`
D. `(B^(2)l^(2)v^(2))/(r ) `