Question

1. which type of signal cannot be used to modulate the output signal?

a sine
b pulse
c square
d triangle

Explanation:

All of sine, pulse, square and triangle signals are commonly - used types of signals for modulation in communication systems. There is no such situation that one of them "cannot be used to modulate the output signal" in general terms. But if we consider in a very restricted or wrong - concept scenario, this might be a mis - stated question. However, based on common knowledge, all these are valid for modulation.

Answer:

There is no correct option as all a. Sine, b. Pulse, c. Square, d. Triangle can be used for modulation.