Except for a brief period immediately after voltage is applied, what can be said about capacitors?

Capacitors are electronic components that store electrical energy in an electric field, and their behavior can be characterized in relation to both direct current (DC) and alternating current (AC). When voltage is applied to a capacitor, it will initially allow current to flow as it begins to charge. However, once it is charged to the supply voltage, it effectively blocks further DC current flow. This is important because it means that while capacitors can store a DC charge, they do not allow a steady DC current to pass through them once fully charged.

In contrast, capacitors have a different interaction with AC current. They do not block AC current in the same manner; instead, they allow the alternating effects of AC to influence the circuit. The capacitor charges and discharges periodically with the AC cycle, thus facilitating the flow of AC current.

Therefore, the correct option captures the dual nature of capacitors, indicating that they block DC current after charging, are capable of storing a DC charge, and can conduct AC effects. This nuanced functionality is critical in various applications, such as smoothing out voltage fluctuations in power supplies and providing coupling or decoupling in signal processing circuits.