A block on a horizontal, frictionless surface is attached to an ideal spring of spring constant \(k\). The block oscillates in simple harmonic motion along the \(x\)-axis, and its position \(x\) as a function of time \(t\) over one complete period \(T\) is shown in the graph. Which of the following graphs best represents the block's acceleration \(a\) as a function of time \(t\) over the same time interval?