The correct option is B perpendicular to the magnetic field.
We know the force (F) acting on the current (I) carrying wire of length (L) kept in a magnetic field (B) at an angle (θ) with the magnetic field is given by
F=ILBsinθ
When θ=90∘⇒sinθ=1= Maximum Value
⇒F=ILB= Maximum Value
So, when the current carrying conductor is placed perpendicular to a magnetic field, it experiences the maximum force.