A parallel-plate capacitor with air between its plates of fixed area \(A\) is connected across an ideal battery that maintains a constant potential difference \(\Delta V_0\). An experimenter slowly increases the plate separation \(d\) starting from an initial value \(d_0\), while keeping the battery connected. A graph of the measured charge \(Q\) on the positive plate as a function of the separation \(d\) is shown.

Which of the following claims correctly relates a feature of the graph to a physical property of the capacitor system?