BOTH INTERNATIONAL & INLAND What shape(s) is/are required to be shown by a vessel aground?

Correct Answer: Option B — Three black balls in a vertical line

Rule 30(d) explicitly mandates that a vessel aground shall exhibit three black balls in a vertical line. This day signal is a critical requirement under both International and Inland Rules, ensuring that other vessels are alerted to the grounded vessel's inability to maneuver, regardless of its size or type.