Correct option is (I) $F=q v B$
Magnetic force $\mathrm{F}=\mathrm{q}(\mathrm{v} \times \mathrm{B})=\mathrm{qvB} \sin \theta$ where $\theta$ is the angle between $v$ and $B$.
Given: $\theta=90^{\circ}$
Thus, force $\mathrm{F}=\mathrm{qvB} \times \sin 90^{\circ}=\mathrm{qvB}$