A Wheel Undergoes Rotational Motion According to the Equation $\phi ( \mathrm { rad } ) = c t + d t ^ { 3 }$

Multiple Choice

A wheel undergoes rotational motion according to the equation $\phi ( \mathrm { rad } ) = c t + d t ^ { 3 }$ , where $\surd$ is in radians, c = 1.0 rad/s, and d = -0.50 rad/s³. The wheel's angular velocity at 2.0 s is

A) -7.0 rad/s.
B) 7.0 rad/s.
C) 5.0 rad/s.
D) -5.0 rad/s.