What does "in step" refer to in regards to towing?

Correct Answer: Option B — Both the towed and towing vessels reach a wave crest or trough at the same time.

Being 'in step' means the towing vessel and the tow are synchronized with the sea state, reaching wave crests or troughs simultaneously. This synchronization minimizes the surge and snap-loading on the hawser, preventing the tow from 'diving' into waves and reducing the risk of hawser failure.