An object attached to an ideal spring undergoes simple harmonic motion along the \(x\)-axis. Its position as a function of time \(t\) is given by \(x(t) = A \cos(\omega t + \phi)\), where \(A\), \(\omega\), and \(\phi\) are positive constants. Which of the following expressions represents the acceleration \(a(t)\) of the object as a function of time?