Concept:The diagram identifies three signal types as input or output based on the direction of data flow.
Explanation:Signal X flows into the system from outside, so it is an input signal.
Signal Y also flows into the system, so it is an input signal.
Signal Z flows out of the system to an external device, so it is an output signal.
Therefore, the order X, Y, Z is input, input, and output.
Answer:D. input, input and output signals.
