I really hope you guys can help me. On the picture below we have 2 signals. Let's call signal X the one that is drawn with a dotted line. The other one we will call signal Y. Now given the 5 options below, where one and only one can be correct, which one would you choose? A) Signal X is analog in continuous time. Signal Y is analog in continuous time quantized. B) Signal X is analog in continuous time. Signal Y is discrete. C) Signal X is discrete. Signal Y is analog in continous time. D) Signal X is discrete quantized. Signal Y is analog in continous time. E) Signal X is in continuous time quantized. Signal Y is discrete. The right answer, according to the people who made the question is (A). I'm not sure if I agree/understand this, and I hope you guys could open my mind. The way I see signal X is analog and signal Y is digital. This is my analysis for each option: A) Wrong because signal Y is not analog (it has a finity number of possible values for its amplitude) [But it says 'quantized'. Is that ok? To be analog AND quantized?] B) Could be correct. Y could be a digital version of signal X, so Y is discrete and quantized, meaning a digital signal. How can I know it is not discrete? I now that if it was just an analog discrete signal it would be shown has a sequence of pulses of very low duration, but if it is a digital signal it would be shown just like it is drawn on the image. C) Can't be correct because signal X is not discrete. D) Same as C. E) Can't be correct because signal X is not quantized. In my opinion this question has answer (B) or none of them. But I could easily been confusing some definitions here (digital, discrete, etc.). I've trying to find those definitions on google but everything was mixed and different from one website to the other. If you guys could give me some help here it would be great. Do you know any books that talk about all of this? I apologize if the question is too simple for you! And sorry for my english!! BR.