A square loop of current$-$carrying wire with edge length a is in the xy plane, the origin being at its center. Along which of the following lines can a charge move without experiencing a magnetic force?

x $=$ a$/2,$ y $=$ a$/2$

x $=0,$ y $=0$

x $=$ a$/2,$ y $=0$

x $=0,$ y $=$ a$/2$

x $=0,$ z $=0$

at any point inside $($the field is uniform$)$

just inside the toroid at its inner surface

just inside the toroid at its outer surface

at none of the above