INTERNATIONAL ONLY You are operating a vessel in a narrow channel. Your vessel must stay within the channel to be navigated safely. Another vessel is crossing your course from starboard to port, and you are in doubt as to his intentions. According to Rule 9, you __________.

A
may sound the danger signal
B
must sound one prolonged and two short blasts
C
should sound one short blast to indicate that you are holding course and speed
D
are required to back down
E