As Shown in the Figure, a Metal Bar Is in Contact

Multiple Choice

As shown in the figure, a metal bar is in contact with a pair of metal parallel rails. A steady uniform magnetic field $B$ , perpendicular to the plane of the rails and pointing outward from the page, is present. The bar is in downward motion with velocity of magnitude $v$ . The direction of the induced current through the resistor $R$ is

A) from $a$ to $b$ .
B) from $b$ to $a$ .
C) No current is induced.