Two long, straight, parallel wires are oriented perpendicular to the xy-plane and carry constant currents in opposite directions. Wire 1 carries current \(I\) out of the page at \((x, y) = (-d, 0)\), and Wire 2 carries current \(2I\) into the page at \((x, y) = (d, 0)\). A magnetic field sensor moved along the x-axis measures the net magnetic field \(\vec{B}\) and detects that it does not vanish at any point in the interval \(-d < x < d\), but drops to zero at exactly one location in the region \(x < -d\). Which of the following correctly explains these measurements?