You are underway on course 142°T when you sight a buoy bearing 105°T. The buoy's white light has a characteristic of continuous very-quick flashing. To ensure that your vessel remains in the best navigable water you would __________.

Correct Answer: Option D — alter course to port and pass north of the buoy

A continuous very-quick flashing light identifies a North cardinal mark. Per IALA standards, cardinal marks indicate the side of the buoy on which the safest water lies. A North cardinal mark signifies that the best navigable water is to the north; therefore, you must alter course to pass north of it.