A wave travels along a stretched string. The provided diagram illustrates the variation of displacement with distance along the string at a particular instant. Interpret the [VISUALIZATION: A detailed sine wave graph representing displacement (y-axis) vs. distance (x-axis). The graph distinctly highlights two key points: Point P, located at the crest (maximum displacement), and Point Q, at the subsequent trough (minimum displacement).] to determine the phase difference between points P and Q?

• A

  0

• B

  (pi/2) rad

• C

  (pi) rad

• D

  (3pi/2) rad