Single pole single throw switch (SPST) is defined as...

• A. An on/off switch that allows current to flow when it is in the closed position.
• B. A two-way switch that directs current along two paths.
• C. A normally closed contact
• D. A normally open contact

Answer: (A)

A basic SPST switch controls a single conductive path between two terminals. It acts as an on/off device: when the contacts are closed, current can flow through the circuit; when they’re open, the circuit is interrupted and no current flows. This directly matches the description of an on/off switch that conducts only in the closed position. The other ideas describe different switch types or states—routing current along multiple paths (which is SPDT or similar) or describing a default contact state (normally open or normally closed), which are not the defining feature of a single-pole single-throw device.