Final answer:
The intensity of a wave is most closely related to its amplitude, with greater amplitude waves having higher intensity. Amplitude is independent of a wave's speed.
Step-by-step explanation:
When assessing the property of a wave that is related to its intensity, the correct answer is its amplitude. A wave's intensity is directly proportional to the square of its amplitude. This means that waves with higher amplitudes will have higher intensities, indicating larger-pressure oscillations both maximally and minimally.
Essentially, when a wave has greater amplitude, the energy it carries is significantly increased, leading to greater intensity. For example, in sounds, this translates to louder noise levels, and in light, to brighter illumination.
The relation between the amplitude of a wave and other properties, such as speed, is important to clarify. The amplitude of a wave is independent of its speed; this means that altering the speed of a wave does not affect its amplitude or consequently its intensity.