A rigid wheel rotates about a fixed horizontal axle through its center. The angular position \(\theta\) of a reference mark on the rim as a function of time \(t\) for \(t \ge 0\) is given by the equation

\[\theta(t) = \theta_0 + bt^2 - ct^3\]

where \(\theta_0\), \(b\), and \(c\) are positive constants. Which of the following graphs best represents the angular acceleration \(\alpha\) of the wheel as a function of time \(t\)?