An analog waveform has two characteristics. Which statement best describes them?

• A. A smooth, continuous line and a rapidly changing frequency
• B. A series of discrete steps and constant amplitude
• C. A smooth, continuous line and a changing amplitude over time
• D. Sharp spikes with no clear pattern

Answer: (D)

Analog waveforms are continuous in time, meaning their value exists at every moment, and they can smoothly vary in amplitude as time passes. The description that fits this best is a smooth, continuous line with amplitude changing over time, because it captures both the time-continuous nature and the changing strength of the signal. Other descriptions point to features that aren’t inherent to all analog signals: discrete steps suggest a digital or sampled signal; sharp spikes with no pattern imply noise or an irregular signal; a line with rapidly changing frequency notes a frequency change, which isn’t a defining trait of all analog waveforms.