The angular momentum L of a rotating object is plotted versus time t. From t=0s to t=2s, the graph is a horizontal line. From t=2s to t=5s, the graph is a straight line with constant negative slope. Which statement best describes the net external torque acting on the object during these two time intervals?
a) It is zero from 0–2 s and constant in magnitude and in the same direction as L from 2–5 s.
b) It is constant and positive from 0–2 s and zero from 2–5 s.
c) It is zero from 0–2 s and constant in magnitude but opposite in direction to L from 2–5 s.
d) It is zero from 0–2 s and increases steadily in magnitude while remaining negative from 2–5 s.