The correct answer is: C. low
A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power. It is composed of semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor’s terminals changes the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits.
The output impedance of a transistor is the resistance that appears between the collector and emitter terminals when the base terminal is open circuit. It is a measure of how much the collector current changes in response to a change in the collector-emitter voltage. The output impedance of a transistor is typically low, which means that it can be used to drive a load with a high current.
Option A is incorrect because the output impedance of a transistor is not high. Option B is incorrect because the output impedance of a transistor is not zero. Option D is incorrect because the output impedance of a transistor is not very low.