Explanation :
A transistor can be used as a switch when the collector-base junction is reverse biased and the emitter-base junction is forward biased. It works in active region.
The width of the base region is small. The doping of the base region is less as compared to the emitter.
Since the base-emitter is forward biased so a large amount of carriers combines at the base region and carried out at the collector region.
This scenario is used as a power amplifier because the output current will be much larger than the input current.
Hence, the correct option is (A) " the output current will be much larger than the input current."
