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

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 ν.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.