Explanation: Lightning strikes and other natural static events are massive, sudden discharges of electrical energy. These discharges create electromagnetic pulses that radiate across a very broad spectrum of radio frequencies. When these pulses are received by an antenna, they cause the *amplitude* or strength of the radio wave to fluctuate dramatically and unpredictably. This characteristic variation in the signal's strength over time is the fundamental definition of Amplitude Modulation (AM). It's essentially broad-spectrum noise where the instantaneous power fluctuates. Options A and B are incorrect because static is broadband noise, containing a wide range of frequencies, not limited to specific odd or even harmonic relationships. The question asks about the *modulation*, not specific frequency components. Option D, Frequency Modulation (FM), involves intentionally varying the *frequency* of a carrier wave to encode information. Natural static's primary impact is on signal strength, making it an amplitude-modulated phenomenon rather than a frequency-modulated one.