What best describes a closed electric circuit?

• A. A circuit that contains no path for current to flow.
• B. A circuit with variable resistance.
• C. A circuit that includes a switch in the open position.
• D. A closed path along which electrons can flow.

Answer: (D)

A closed electric circuit is a complete loop that lets current flow continuously from the power source, through conductors and any loads, and back to the source. The key idea is that the path must be unbroken so charges can keep moving; if there's a break, the circuit is open and current stops. Describing it as a closed path along which electrons can flow captures both the existence of a continuous route and the movement of charge. The other scenarios either lack a complete path (no path for current), depend on a component state rather than being closed by design (a switch in the open position), or merely involve changing resistance without guaranteeing that the loop is intact.