The electronic circuit shown in the figure represents a 

detailed solution

Correct option is C

When A is connected to ground, base emitter junction is not forward based so the transistor will not conduct and current through R0 is zero. Hence V0=5 volt is when A = 0, Y = 1. Again when A is connected to P, base-emitter junction is forward biased and collector-emitter junction is reverse biased. So the transistor conducts and current through R0 is equal to 5R0. In this case V0=5−I0.R0=5−5R0R0=0. So when A=1, Y=0. Hence the circuit represents a NOT gate