What type of switch has one input terminal and one output?

The correct answer is based on the definition and functionality of a SPST switch, which stands for Single Pole Single Throw. This type of switch has one input terminal and one output terminal, making it the simplest form of switch configuration. It is designed to connect or disconnect the circuit, effectively allowing current to flow through when the switch is in the "on" position, and stopping the current when it is in the "off" position.

The SPST switch is commonly used in basic applications where a simple on-off control is needed, such as in light switches or to control devices without requiring additional configurations or terminals.

In contrast to other options, a DPDT switch, or Double Pole Double Throw, allows for more complex circuits through multiple input and output pathways, while an SPDT (Single Pole Double Throw) can direct the current to one of two different outputs but still has more complexity than what is typically needed for single input and output connections. A three-way switch is used in scenarios where you want to control a single load from two different locations, requiring additional terminals and connections, thus differing from the simplicity of the SPST design.