A car is moving in a circular horizontal track of radius $10 \mathrm{~m}$ with a constant speed of $10 \mathrm{~m} / \mathrm{s}$. A plumb bob is suspended from the roof of the car by a light rigid rod of length $1 \mathrm{~m}$. The angle made by the rod with the track is:
(a) zero
(b) $30^{\circ}$
(c) $45^{\circ}$
(d) $60^{\circ}$