BOTH INTERNATIONAL & INLAND How long is the duration of a prolonged blast of the whistle?

Correct Answer: Option B — 4 to 6 seconds

Rule 32(c) defines a prolonged blast as a blast of from 4 to 6 seconds duration. This standard duration is critical for the consistent interpretation of sound signals used in restricted visibility and for maneuvering and warning signals as prescribed throughout the International and Inland Navigation Rules.