A Small Car of Mass M Travels Along a Straight

Multiple Choice

A small car of mass M travels along a straight, horizontal track. As suggested in the figure, the track then bends into a vertical circle of radius R.
-Which one of the following expressions determines the minimum speed that the car must have at the top of the track if it is to remain in contact with the track?

A) v = MgR
B) v = 2gR
C) v² = 2gR
D) v² = gR
E) v = gR