Answer
Standing waves are produced by the superposition of two waves with
(b) the same amplitude and frequency, and opposite propagation directions.
Work Step by Step
In order to create standing waves (waves that do not move left or right), the two waves must be moving in opposite directions.
In order to create nodes, which are points that do not move, the two waves must have the same amplitude and the same frequency.
Standing waves are produced by the superposition of two waves with
(b) the same amplitude and frequency, and opposite propagation directions.
