INTERNATIONAL ONLY When two vessels are in sight of one another, all of the following signals may be given EXCEPT __________.

Correct Answer: Option D — four short whistle blasts

COLREG Rule 35(e) prescribes four short blasts specifically for pilot vessels engaged on pilotage duty in restricted visibility. When vessels are in sight of one another in normal visibility, four short blasts are not a valid maneuvering signal.