In which case would an overtaking vessel sound a whistle signal of two prolonged followed by one short blast?

A、 When overtaking in restricted visibility.
B、 When overtaking in a narrow channel（RULE34 3 （1）2长1短：我船企图从你船右舷追越；（2）2长2短：我船企图从你船左舷追越）
C、 When overtaking on open waters.
D、 When no other vessels are in the immediate area.