Final answer:
Destructive interference occurs when the crest of one wave combines with the trough of another, resulting in a cancellation that leads to a net amplitude of zero.
Step-by-step explanation:
In destructive interference, the components of waves that combine are a crest and a trough. When the peak of one wave aligns with the trough of another wave of the same frequency and amplitude, but with opposite phases, they cancel each other out. This results in a net amplitude of zero, the world line of a particle provides a broader perspective in spacetime. A stationary particle has a world line that is a vertical line parallel to the time axis, while the world line for a particle with constant velocity is a straight line inclined to the time axis which we observe as destructive interference. The correct answer to the question is d) Crest and trough.