Compressions in longitudinal sound waves occur at maximum particle density.

Steps:

• Identify sound as a longitudinal wave where particles oscillate parallel to propagation.
• Note the graph plots particle displacement versus distance at a fixed time.
• Recognize compressions as regions of high density, corresponding to steep negative slopes in the displacement-distance graph.
• Locate the point with the most negative slope, which is the center of compression.

Why B is correct:

• Point B shows the steepest negative slope, where dx/dy is minimized, indicating maximum compression per the wave equation for longitudinal waves.

Why the others are wrong:

• A: Positive slope indicates rarefaction (low density).
• C: Near-zero slope represents equilibrium, not compression.
• D: Gentle negative slope is edge of compression, not center.

Final answer: B