A standing wave is established on a stretched string fixed at both ends. Which statement best explains why the displacement of the string at a node remains zero at all times?
(a) Tension is maximum at a node, forcing that point to stay at its equilibrium position.
(b) Energy cannot exist at a node, so the string is physically prevented from moving there.
(c) At a node, the two traveling waves have equal amplitudes but opposite displacements for every instant, so their superposition is always zero.
(d) Destructive interference occurs only once each cycle at a node, but the string stays at rest there for the whole time due to its inertia.