Two Very Long Parallel Wires in the Xy-Plane,a Distance 2a

Multiple Choice

Two very long parallel wires in the xy-plane,a distance 2a apart,are parallel to the y-axis and carry equal currents I as shown in the figure.The +z direction points perpendicular to the xy-plane in a right-handed coordinate system.If the left current flows in the +y direction and the right current flows in the -y direction,which one of the graphs shown in the figure below best represents the z component of the net magnetic field,in the xy-plane,as a function of x? (Caution: These graphs are not magnetic field lines.)

A) 1
B) 2
C) 3
D) 4
E) 5