Question

multiple choice question
signals that do not vary in size but change in how often they occur are referred to as _____-modulated signals.
o frequency
o amplitude

Explanation:

Frequency - modulation changes the frequency of the carrier wave according to the message signal, while amplitude - modulation changes the amplitude. Since the question refers to changes in how often (frequency) they occur and not in size (amplitude), the answer is frequency - modulated.

Answer:

frequency