The presence of an object is signalled by which type of output from a PNP transistor?

In a PNP transistor, the flow of current is controlled by the presence of a voltage signal at its base. When a PNP transistor is "on" or conducting, it allows current to flow from the collector to the emitter. This state indicates the presence of an object because the transistor is providing a high output signal, typically close to the supply voltage.

When the base is supplied with a lower voltage relative to the emitter, the transistor turns on, resulting in a high output. This high output confirms that a connected device or system can detect the presence of the object. In applications like sensors or switches, this high output state effectively communicates that the circuit is activated and the object detection is successful.

Thus, in the context of the question, the correct choice of a high output is indicative of the presence of an object as it aligns with the functioning principle of a PNP transistor.